The m odern use of Ancient Greek and Roman Theatres …etd.dtu.dk/thesis/193464/oersted_dtu2877.pdf · TECHNICAL UNIVERSITY OF DENMARK Acoustic Technology Ørsted DTU By Konstantinos

TECHNICAL UNIVERSITY OF DENMARK

Acoustic Technology

Ørsted●DTU

By Konstantinos Angelakis

The modern use of Ancient Greek and Roman Theatres from an acoustic point of view

Supervised by Jens Holger Rindel and Anders Christian Gade

October 2006

The modern use of Ancient Greek and Roman theaters from an acoustic point of view

2

Acknowledgements

At this point I would like to acknowledge the people who contributed in the

realization of this project;

• Jens Holger Rindel, for supervising the project

• Anders Christian Gade, for supervising the project, as well as providing

guiding and assistance during the measurements in Greece

• Paris Kerketsos, for all the help and support during the measurements, as well

as for modeling the theatres in ODEON

• Lazaridou Varvara (responsible for the performances at the Theatre of

Epidauros), for the smooth collaboration and assistance

• Kazolias Nikos (responsible engineer for both theatres), for the smooth

collaboration and assistance

• Jørgen Rasmussen, for the technical support whenever I needed it, in Denmark

• Periklis Mathiellis, for the technical support in Greece

• Torben Poulsen, for his advice on matters related to the listening tests

• My colleagues who voluntarily participated in the listening tests

• My colleagues Jorge Alvarez, Konca Saher and Shen Yi, for their advice and

friendship

• My housemates for supporting me through the whole process. Specifically,

Mihalis Kampanis for keeping me company during the long nights when I was

writing this report, as well as for proofreading the whole document!

• Candela Torres, for helping in the recordings.

This project is the epilogue of a two year effort in specializing in the world of

acoustics. Given the opportunity, apart from thanking the professors of the department

of Acoustic Technology at DTU, who guided me through the different paths of

acoustics, I would like to acknowledge my family for always providing a steady base

where I could psychologically rely on. I would like to express my gratitude to:

• My grandmother Eleftheria for her uncompromised love

• My sister Olga for sharing her philosophical worries with me, and my brother

Minas for his medical advice

• My mother Violetta for her support and affection

• My father Thanassis for purifying and strengthening my motivation to study

acoustics by being opposite to my decision, at least at the beginning.


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CONTENTS

1. INTRODUCTION AND OBJECTIVES.........................................................9

2. INFORMATION ON THE THEATRES UNDER INVESTIGATION...11

2.1. THE THEATRE OF EPIDAUROS .............................................................................................11 2.2. THE THEATRE OF ANCIENT EPIDAUROS.............................................................................12 2.3. CONTEMPORARY USE OF THE THEATRES ............................................................................12

3. DESCRIPTION OF ACOUSTIC MEASUREMENTS AND RECORDINGS .........................................................................................................14

3.1. ACOUSTIC MEASUREMENTS ................................................................................................14 3.1.1. Equipment ............................................................................................14

3.1.2. Calibration............................................................................................16

3.1.3. Procedure..............................................................................................17 3.2. RECORDINGS .......................................................................................................................21

3.2.1. Equipment ............................................................................................21

3.2.2. Calibration............................................................................................21

3.2.3. Procedure..............................................................................................22

4. DESCRIPTION OF THE MODELS..............................................................25

5. MEASUREMENTS AND SIMULATIONS.................................................29

5.1. THEATRE OF EPIDAUROS-RESULTS AND DISCUSSION.........................................................29

5.1.1. Comparison of source positions ...........................................................29

5.1.2. Evaluation of the model .......................................................................35

5.1.3. Addition of a stage ...............................................................................44 5.2. THEATRE OF ANCIENT EPIDAUROS-RESULTS AND DISCUSSION ........................................48 5.2.1. Comparison of source positions ...........................................................48

5.2.2. Evaluation of the model .......................................................................53

5.2.3. Addition of a stage ...............................................................................62

6. LISTENING TESTS .........................................................................................66

6.1. RESULTS AND DISCUSSION ..................................................................................................67 6.1.1. Section 1...............................................................................................67

6.1.2. Section 2...............................................................................................73

7. CONCLUSIONS AND FUTURE WORK ....................................................76

7.1. CONCLUSIONS .....................................................................................................................76 7.2. FUTURE WORK .....................................................................................................................78

8. REFERENCES ...................................................................................................79

9. APPENDIX.........................................................................................................80

9.1. T30 VERSUS T20...................................................................................................................80 9.2. THE EFFECT OF THE GROUND ..............................................................................................83 9.3. THEATRE OF EPIDAUROS- GRID RESPONSE ODEON PLOTS..............................................90 9.4. THEATRE OF ANCIENT EPIDAUROS-GRID RESPONSE ODEON PLOTS ..............................95

10. GLOSSARY .................................................................................................100


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LIST OF FIGURES

Figure 2.1: A view of the Theatre of Epidauros......................................................................................11 Figure 2.2: A view of the Theatre of Ancient Epidauros ........................................................................12 Figure 3.1: The measuring equipment (except from the source and receiver). .......................................14 Figure 3.2: While recording an impulse response at the Theatre of Epidauros. The microphone and the

loudspeaker can be seen at the right and upper left of the photograph, respectively.....................15 Figure 3.3: The setup used for obtaining the data used for calibration of the measuring system. ..........16 Figure 3.4: Plan view of the Theatre of Epidauros. The receiver positions are marked with black dots.

The letters and numbers reveal the coding that was chosen for the receiver positions (eg. A5,

C15, U15 etc.). ..............................................................................................................................17 Figure 3.5: Plan view of the orchestra and skene of Theatre of Epidauros. The source positions are

marked with red dots. The letters and numbers reveal the coding that was chosen for the source

positions (S1, S2 and S3). .............................................................................................................18 Figure 3.6: Setting up source position S2. ..............................................................................................18 Figure 3.7: Plan view of the Theatre of Ancient Epidauros. The receiver positions are marked with

black dots. The letters and numbers reveal the coding that was chosen for the receiver positions

(eg. A2, C8, E14 etc.). ...................................................................................................................19 Figure 3.8: The wooden construction that was built on top of the orchestra and skene of the Theatre of

Ancient Epidauros during the time that the measurements were conducted. ................................20 Figure 3.9: Plan view of the orchestra and skene of Theatre of Epidauros. The source positions are

marked with red dots. The letters and numbers reveal the coding that was chosen for the source

positions (S1, S2 and S3). .............................................................................................................20 Figure 3.10: The pair of “home-made”, binaural microphones that were used for the conduction of the

recordings at one of the positions. .................................................................................................21 Figure 3.11: The red circles indicate the recording positions at the Theatre of Epidauros. ....................22 Figure 3.12: The red circles indicate the recording positions at the Theatre of Ancient Epidauros........23 Figure 3.13: Two very different stage setups at the Theatre of Epidauros; on the left picture the stage

setup for the “Persians” and on the right picture the stage setup for the “Suppliants”. .................24 Figure 4.1: The model of the Theatre of Epidauros. The surrounding box is totally absorbing, in an

effort to simulate “open-air” conditions. .......................................................................................25 Figure 4.2: The model of the Theatre of Ancient Epidauros...................................................................26 Figure 4.3: Rough sketches and the dimensions of the stage buildings. .................................................27 Figure 4.4: The model of the Theatre of Epidauros with the added stage building. ...............................28 Figure 4.5: The model of the Theatre of Ancient Epidauros with the added stage building. ..................28 Figure 5.1: Strength (G) versus distance at the Theatre of Epidauros. Each point represents the average

of the values at 500Hz and 1000Hz octave bands, for the specific source-receiver setup [8]. ......30 Figure 5.2: Early Decay Time (EDT) versus distance at the Theatre of Epidauros. Each point represents

the average of the values at 500Hz and 1000Hz octave bands, for the specific source-receiver

setup [8].........................................................................................................................................31 Figure 5.3: Speech Transmission Index (STI) versus distance at the Theatre of Epidauros. Each point

represents the average of the values at 500Hz and 1000Hz octave bands, for the specific source-

receiver setup [8]. ..........................................................................................................................32 Figure 5.4: Reverberation Time (T30) versus distance at the Theatre of Epidauros. Each point


receiver setup [8]. ..........................................................................................................................33 Figure 5.5: Reverberation Time (T30) versus frequency at the Theatre of Epidauros. Each point

represents the average of the values measured in all receiver positions, for the specific octave

band. The different colors indicate the position of the sound source; blue, pink, green correspond

S1, S2 and S3, respectively. ..........................................................................................................33 Figure 5.6: Reverberation Time (T30) versus frequency at the Theatre of Epidauros. The source is

positioned in the center of the orchestra. Each point represents the average of the values

measured in all receiver positions, for the specific octave band. The pink and blue line, indicate

the measured and simulated values, respectively. .........................................................................35 Figure 5.7: Strength (G) versus frequency for 3 different receiver positions at the Theatre of Epidauros.

The source is located in the center of the orchestra. The solid and dotted lines indicate measured

and simulated values, respectively. ...............................................................................................36 Figure 5.8: Reverberation Time (T30) versus distance at the Theatre of Epidauros. The source is

positioned in the center of the orchestra. Each point represents the average of the values at 500Hz


5

and 1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots indicate

the measured and simulated values, respectively. .........................................................................37 Figure 5.9: Strength (G) versus distance at the Theatre of Epidauros. The source is positioned in the

center of the orchestra. Each point represents the average of the values at 500Hz and 1000Hz

octave bands, for the specific receiver position [8]. The pink and blue dots indicate the measured

and simulated values, respectively. ...............................................................................................38 Figure 5.10: Early Decay Time (EDT) versus distance at the Theatre of Epidauros. The source is



the measured and simulated values, respectively. .........................................................................39 Figure 5.11: The simulated and integrated decay curves at 1000Hz produced by ODEON, for position

A25. ...............................................................................................................................................40 Figure 5.12: The simulated and integrated decay curves at 1000Hz produced by ODEON, for position

C25. ...............................................................................................................................................40 Figure 5.13: The direction of reflections responsible for the increase of the energy at 113msec at

position A25, according to ODEON..............................................................................................41 Figure 5.14: Clarity (C80) versus distance at the Theatre of Epidauros. The source is positioned in the



and simulated values, respectively. ...............................................................................................42 Figure 5.15: Speech Transmission Index (STI) versus distance at the Theatre of Epidauros. The source

is positioned in the center of the orchestra. Each point represents the average of the values at

500Hz and 1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots

indicate the measured and simulated values, respectively.............................................................43 Figure 5.16: Reverberation Time (T30) versus distance at the Theatre of Epidauros. The source is



values obtained from the model of the theatre with and without stage, respectively. ...................44 Figure 5.17: Strength (G) versus distance at the Theatre of Epidauros. The source is positioned in the


octave bands, for the specific receiver position [8]. The pink and blue dots indicate values

obtained from the model of the theatre with and without stage, respectively. ..............................45 Figure 5.18: Early Decay Time (EDT) versus distance at the Theatre of Epidauros. The source is



values obtained from the model of the theatre with and without stage, respectively. ...................45 Figure 5.19: Clarity (C80) versus distance at the Theatre of Epidauros. The source is positioned in the



obtained from the model of the theatre with and without stage, respectively. ..............................46 Figure 5.20: Speech Transmission Index (STI) versus distance at the Theatre of Epidauros. The source



indicate values obtained from the model of the theatre with and without stage, respectively.......46 Figure 5.21: Strength (G) versus distance at the Theatre of Ancient Epidauros. Each point represents

the average of the values at 500Hz and 1000Hz octave bands, for the specific source-receiver

setup [8].........................................................................................................................................48 Figure 5.22: Early Decay Time (EDT) versus distance at the Theatre of Ancient Epidauros. Each point


receiver setup [8]. ..........................................................................................................................49 Figure 5.23: Speech Transmission Index (STI) versus distance at the Theatre of Ancient Epidauros.

Each point represents the average of the values at 500Hz and 1000Hz octave bands, for the

specific source-receiver setup [8]. .................................................................................................50 Figure 5.24: Reverberation Time (T30) versus distance at the Theatre of Epidauros. Each point


receiver setup [8]. ..........................................................................................................................51 Figure 5.25: Reverberation Time (T30) versus frequency at the Theatre of Ancient Epidauros. Each

point represents the average of the values measured in all receiver positions, for the specific

octave band. The different colors indicate the position of the sound source; blue, pink, green

correspond S1, S2 and S3, respectively.........................................................................................51


6

Figure 5.26: Reverberation Time (T30) versus frequency at the Theatre of Ancient Epidauros. The

source is positioned in the center of the orchestra. Each point represents the average of the values


the measured and simulated values, respectively. .........................................................................53 Figure 5.27: Strength (G) versus frequency at the Theatre of Ancient Epidauros. The source is

positioned in the center of the orchestra. The solid and dotted lines indicate the measured and

simulated values, respectively. ......................................................................................................54 Figure 5.28: Reverberation Time (T30) versus distance at the Theatre of Ancient Epidauros. The source



indicate the measured and simulated values, respectively.............................................................55 Figure 5.29: Strength (G) versus distance at the Theatre of Ancient Epidauros. The source is positioned

in the center of the orchestra. Each point represents the average of the values at 500Hz and

1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots indicate the

measured and simulated values, respectively. ...............................................................................56 Figure 5.30: Early Decay Time (EDT) versus distance at the Theatre of Ancient Epidauros. The source



indicate the measured and simulated values, respectively.............................................................56 Figure 5.31: Early Decay Time (EDT) versus the number of the kerkida at the Theatre of Ancient

Epidauros (1 to 5 corresponds from A to E respectively). The source is positioned in the center of

the orchestra. Each point represents the average of the values at 500Hz and 1000Hz octave bands,

for the specific receiver position [8]. All points indicate measured values. ..................................57 Figure 5.32: View of the Theatre of Ancient Epidauros at the time of the measurements......................58 Figure 5.33: Early Decay Time (EDT) versus the number of the kerkida at the Theatre of Ancient


the orchestra. Each point represents the average of the values at 500Hz and 1000Hz octave bands,

for the specific receiver position [8]. The solid and dotted lines indicate the measured and

simulated values, respectively. ......................................................................................................58 Figure 5.34: Clarity (C80) versus distance at the Theatre of Ancient Epidauros. The source is



the measured and simulated values, respectively. .........................................................................59 Figure 5.35: Clarity (C80) versus the number of the kerkida at the Theatre of Ancient Epidauros (1 to 5

corresponds from A to E respectively). The source is positioned in the center of the orchestra.


specific receiver position [8]. The solid and dotted lines indicate the measured and simulated

values, respectively. ......................................................................................................................60 Figure 5.36: Speech Transmission Index (STI) versus distance at the Theatre of Ancient Epidauros. The


at 500Hz and 1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots

indicate the measured and simulated values, respectively.............................................................61 Figure 5.37: Reverberation Time (T30) versus distance at the Theatre of Ancient Epidauros. The source



indicate values obtained from the model of the theatre with and without stage, respectively.......62 Figure 5.38: Strength (G) versus distance at the Theatre of Ancient Epidauros. The source is positioned


1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots indicate

values obtained from the model of the theatre with and without stage, respectively. ...................63 Figure 5.39: Early Decay Time (EDT) versus distance at the Theatre of Ancient Epidauros. The source



indicate values obtained from the model of the theatre with and without stage, respectively.......63 Figure 5.40: Clarity (C80) versus distance at the Theatre of Ancient Epidauros. The source is



values obtained from the model of the theatre with and without stage, respectively. ...................64 Figure 5.41: Speech Transmission Index (STI) versus distance at the Theatre of Ancient Epidauros. The



7


indicate values obtained from the model of the theatre with and without stage, respectively.......64 Figure 6.1: The recording positions at the Theatre of Epidauros. The red characters indicate the code

letters of the positions chosen for the purpose of the listening tests. The black characters indicate

the exact position; the letter corresponds to the kerkida and the number to the row. The recording

position was chosen to be approximately in the middle of the respective row..............................67 Figure 6.2: The percentage of the test subjects versus their answers. The performance was not

amplified and it took place at the Theatre of Epidauros. ...............................................................68 Figure 6.3: The percentage of the test subjects versus their answers. The performance was amplified

and it took place at the Theatre of Epidauros. ...............................................................................69 Figure 6.4: The recording positions at the Theatre of Epidauros. The red characters indicate the code

letters of the positions chosen for the purpose of the listening tests. The black characters indicate

the exact position; the letter corresponds to the kerkida and the number to the row. The recording

position was chosen to be approximately in the middle of the respective row..............................70 Figure 6.5: The percentage of the test subjects versus their answers. The performance was not

amplified and it took place at the Theatre of Ancient Epidauros. .................................................71 Figure 6.6: The percentage of the test subjects versus their answers. The performance was amplified

and it took place at the Theatre of Ancient Epidauros...................................................................71 Figure 9.1: Reverberation Time versus distance at the Theatre of Epidauros. The source is positioned in

the center of the orchestra. Each point represents the average of the values at 500Hz and 1000Hz

octave bands, for the specific receiver position [8]. The pink and blue line, indicate the measured

values for T20 and T30, respectively. ...........................................................................................80 Figure 9.2: Reverberation Time versus frequency at the Theatre of Epidauros. The source is positioned

in the center of the orchestra. Each point represents the average of the values measured in all

receiver positions, for the specific octave band. The pink and blue line, indicate the measured

values for T20 and T30, respectively. ...........................................................................................81 Figure 9.3: Reverberation Time versus distance at the Theatre of Ancient Epidauros. The source is


and 1000Hz octave bands, for the specific receiver position [8]. The pink and blue line, indicate

the measured values for T20 and T30, respectively. .....................................................................81 Figure 9.4: Reverberation Time versus frequency at the Theatre of Ancient Epidauros. The source is



the measured values for T20 and T30, respectively. .....................................................................82 Figure 9.5: The receiver (red dot on black line) receives both the direct sound and the reflection coming

from the orchestra floor. The black dot on the solid black line and the black dot on the dashed

line indicate the real and the image source, respectively. The notations HS, HR and D stand for

“Height of Source from the ground”, “Height of Receiver from the ground” and “Horizontal

Distance between Source and Receiver”, respectively. .................................................................84 Figure 9.6: The effect of the interference of the direct sound and the reflection coming from the floor of

the orchestra, on the sound pressure measured at the 5th row of the Theatre of Epidauros. The

floor of the orchestra is considered totally reflecting. ...................................................................85 Figure 9.7: The effect of the interference of the direct sound and the reflection coming from the floor of






floor of the orchestra is considered totally reflecting. ...................................................................87 Figure 9.10: The effect of the interference of the direct sound and the reflection coming from the floor

of the orchestra, on the sound pressure measured at the 38th row of the Theatre of Epidauros. The

floor of the orchestra is considered totally reflecting. ...................................................................87 Figure 9.11: The effect of the interference of the direct sound and the reflection coming from the floor

of the orchestra, on the sound pressure measured at the 2nd row of the Theatre of Ancient

Epidauros. The floor of the orchestra is considered totally reflecting. ..........................................88 Figure 9.12: The effect of the interference of the direct sound and the reflection coming from the floor

of the orchestra, on the sound pressure measured at the 8th row of the Theatre of Ancient

Epidauros. The floor of the orchestra is considered totally reflecting. ..........................................89


8

Figure 9.13: The effect of the interference of the direct sound and the reflection coming from the floor

of the orchestra, on the sound pressure measured at the 14th row of the Theatre of Ancient

Epidauros. The floor of the orchestra is considered totally reflecting. ..........................................89 Figure 9.14: Early Decay Time (EDT) at 1000Hz at the Theatre of Epidauros (without stage). ............90 Figure 9.15: Early Decay Time (EDT) at 1000Hz at the Theatre of Epidauros (with stage). .................90 Figure 9.16: Reverberation Time (T30) at 1000Hz at the Theatre of Epidauros (without stage). ..........91 Figure 9.17: Reverberation Time (T30) at 1000Hz at the Theatre of Epidauros (with stage).................91 Figure 9.18: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Epidauros (without stage). .......92 Figure 9.19: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Epidauros (with stage). ............92 Figure 9.20: Clarity (C80) at 1000Hz at the Theatre of Epidauros (without stage). ...............................93 Figure 9.21: Clarity (C80) at 1000Hz at the Theatre of Epidauros (with stage). ....................................93 Figure 9.22: Speech Transmission Index (STI) at 1000Hz at the Theatre of Epidauros (without stage).

.......................................................................................................................................................94 Figure 9.23: Speech Transmission Index (STI) at 1000Hz at the Theatre of Epidauros (with stage). ....94 Figure 9.24: Early Decay Time (EDT) at 1000Hz at the Theatre of Ancient Epidauros (without stage).

.......................................................................................................................................................95 Figure 9.25: Early Decay Time (EDT) at 1000Hz at the Theatre of Ancient Epidauros (with stage). ...95 Figure 9.26: Reverberation Time (T30) at 1000Hz at the Theatre of Ancient Epidauros (without stage).

.......................................................................................................................................................96 Figure 9.27: Reverberation Time (T30) at 1000Hz at the Theatre of Ancient Epidauros (with stage). ..96 Figure 9.28: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Ancient Epidauros (without

stage). ............................................................................................................................................97 Figure 9.29: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Ancient Epidauros (with stage).

.......................................................................................................................................................97 Figure 9.30: Clarity (C80) at 1000Hz at the Theatre of Ancient Epidauros (without stage)...................98 Figure 9.31: Clarity (C80) at 1000Hz at the Theatre of Ancient Epidauros (with stage)........................98 Figure 9.32: Speech Transmission Index (STI) at 1000Hz at the Theatre of Ancient Epidauros (without

stage). ............................................................................................................................................99 Figure 9.33: Speech Transmission Index (STI) at 1000Hz at the Theatre of Ancient Epidauros (with

stage). ............................................................................................................................................99

LIST OF TABLES

Table 6.1: General information for the performances.............................................................................67 Table 6.2: Pairs that were compared in Section 2 of the listening tests. The colors stress whether the

performance was amplified (light orange) or not (light yellow). Large = Theatre of Epidauros,

Small = Theatre of Ancient Epidauros. .........................................................................................74 Table 6.3: The values of the acoustic quantities measured in the receiver positions which are the closest

to the recording positions used for this part of the listening tests..................................................75 Table 9.1: Table of values for the Theatre of Epidauros.........................................................................84 Table 9.2: Table of values for the Theatre of Ancient Epidauros. ..........................................................88

Introduction and objectives

9

1. Introduction and objectives

Greek and Roman theatres have undoubtedly played an important role not only in the

society of their times but also today. In fact, many of those theatres are used

nowadays, if their present condition allows it. The intensive contemporary use of

ancient theatres has given rise to discussions -in national and international level- that

range from practical issues (e.g. maintenance and restoration of the theatres) to

theoretical aspects regarding their use (e.g. type and content of the performances that

take place in those spaces in respect to the protection and preservation of cultural

heritage). These topics have been addressed in several international charters ([1], [2],

[3]) related to world cultural heritage. The acoustic properties of open-air theatres are

also discussed in those charters, since they consist of functional characteristics of

those spaces and their investigation is by itself of great importance from a cultural and

educational point of view.

However, considering the intensive contemporary use of ancient theatres there is a

need for directing investigation efforts towards addressing specific issues related to

their acoustics; what can be done in order to restore the acoustical properties of the

theatres, if and how can they be improved, in which extent can amplification be used

in modern performances etc.

Part of the objectives of the “ERATO”1 project was to process and discuss some of

these topics. Under “ERATO”, acoustic measurements and computer simulations of

ancient Greek and Roman theatres were conducted. The theatres that were included

were located in Italy, Turkey and Jordan. In the outcomes of “ERATO” [4], specific

recommendations and guidelines have been proposed concerning the modern use of

the theatres [5].

For the purpose of evaluating these recommendations and more specifically the ones

that suggest “restoration of the stage” and “positioning of the sound sources on the

proscenium near the skene wall”, it was decided to study two cases of theatres, which

this time would be located in Greece.

1 “Identification, Evaluation and Revival of the Acoustical heritage of ancient Theatres and Odea”: An

EU funded program with a duration of 3 years, in which the Department of Acoustic Technology at

DTU was involved.

Introduction and objectives

10

The first theatre that was chosen was the Theater of the Sanctuary of Asklepios at

Epidauros (from now on referred to as “Theater of Epidauros”) since it is a typical

example of an ancient Greek theatre of the Hellenistic period2 and it is the best

preserved of its kind. The second theatre investigated was the, much smaller, Theatre

of Ancient Epidauros, the construction of which dates back to the 4th century BC;

however, it took its final form during the Roman era3 and it is preserved in this form

until today. Both theatres are used intensively nowadays and the types of

performances that they host vary from modern versions of Ancient Greek

tragedies/comedies to musical concerts.

In those theatres a set of in situ acoustic measurements were conducted in various

source-receiver configurations. The aim was to obtain data that would allow

comparisons among different source positions. Furthermore, those measurements

were compared to simulations of the theatres created with the use of the ODEON

software. After obtaining a satisfactory agreement between the measured and

simulated data the models were used in order to investigate the effect of the addition

of a stage in the acoustic behavior of the theatres. Finally, in an attempt to approach

the effect of amplification on subjective aspects of the acoustical character of the

theatres (e.g. the perception of space based only on auditory cues, intimacy) a series

of listening tests was conducted. The relation of the observations with objectively

measured acoustic parameters (e.g. Sound Pressure Level, Clarity) was also

investigated. The material (i.e. the audio tracks) used for the purpose of the tests was

obtained from binaural recordings of amplified and non amplified performances in

both theatres.

The outcomes of the present study are expected to give an insight to the acoustical

behavior of the theatres under investigation, as well as to expand the analysis already

carried out in the duration of the ERATO project. Last but not least, by combining the

use of “tools” like objective measurements, computer simulations and listening tests,

this study’s most ambitious goal is to point out a more complete way of approaching

the matter of contemporary use.

The terms written in italics are Greek (Hellenic) or Latin terms related to the theatres

and they are explained in the Glossary.

2 4th to 1

st century BC

3 Starting around the 2

nd or 1

st century BC

Information on the theatres under investigation

11

2. Information on the theatres under investigation

2.1. The Theatre of Epidauros

The Theatre of Epidauros is situated at the North-West part of Peloponnesos in

Greece. It is a typical example of a theatre of its time, consisting of the basic parts of

the ancient Greek theatre; the Koilon, the Orchestra, the Skene. It was built in two

stages; the lower part of the koilon (below the diazoma), the orchestra and the skene

were built around the 4th century B.C. The extension of the koilon was made around

the middle of the 2nd century B.C. An idea about the size of the construction can be

obtained if we take into account that the longest radius of the koilon is 58m and the

diameter of the orchestra is about 20m. The capacity of the theatre is about 13000

to14000 spectators

The theatre was used for solo singing, chanting, musical/poetical contests (mainly for

solo instruments) and theatrical performances of ancient tragedies and comedies.

Figure 2.1: A view of the Theatre of Epidauros


12

2.2. The Theatre of Ancient Epidauros

The Theatre of Ancient Epidauros is situated about 12 km further away from the

Theatre of Epidauros, in a small city called Ancient Epidauros. It was discovered

rather recently (1970) and the excavations are still in process nowadays. It was

constructed in sections and it is speculated that it had a simple initial form. The

theatre was built in the middle of the 4th century B.C. and the constructions continued

until the Hellenistic times, but later during the Roman period, the orchestra became

semi-circular with the erection of a stage nearer to the koilon, of which only the lower

part has survived until now. The theatre could host 2000 spectators, although today’s

capacity is around 500.

The Theatre of Ancient Epidauros had been in use for centuries along with the

Theatre of Epidauros.

Figure 2.2: A view of the Theatre of Ancient Epidauros

2.3. Contemporary use of the theatres

Nowadays, during the summer season both theatres host a variety of performances.

The performances usually relate in some way with the ancient Greek theatrical

heritage, especially in the case of the Theatre of Epidauros.

Since, in both theatres under investigation only the ruins of the skene survive until

today, the construction of a temporary stage building is often required. In the case of

the Theatre of Epidauros it depends on the production and the characteristics of the


13

construction can vary widely, from a simple wooden panel to a complicated and full

size skene. At the Theatre of Ancient Epidauros on the other hand a temporary

wooden platform covering the orchestra and the stage is installed every year for the

period that the performances take place.

Although there are still productions in which no artificial amplification of the voices

of the actors (or of musical instruments) is used, the number of productions that

experiment with the use artificial amplification is increasing. At the Theatre of

Ancient Epidauros most of the presented performances are amplified.

Description of acoustic measurements and recordings

14

3. Description of acoustic measurements and recordings

3.1. Acoustic measurements

3.1.1. Equipment

For the measurements the DIRAC software v3.0 was used, running on a portable

computer. The source was a dodecahedron loudspeaker and the receiver was an AKG

stereo microphone. A pre-amplifier, an amplifier and the necessary cabling between

the devices were used as well.

The signal that was used was an exponential sweep with a duration of 10,9 seconds.

The signal was produced by the DIRAC software and it was first fed to the pre-

amplifier and amplifier and then directed to the loudspeaker. The microphone was

also connected to the laptop and the impulse responses in different positions of the

theatres were recorded.

Figure 3.1: The measuring equipment (except from the source and receiver).


15

Figure 3.2: While recording an impulse response at the Theatre of Epidauros. The microphone

and the loudspeaker can be seen at the right and upper left of the photograph, respectively.


16

3.1.2. Calibration

For the calibration of our measuring system the following setup was used. The source

(dodecahedron loudspeaker) and receiver (AKG microphone) were positioned at a

height of 1,5m and the distance between them was 2m4.

Mineral wool was placed between them (in parallel to the ground plain and covering a

surface of about 2m2) at a height of 0,4 m, in order to absorb the reflections coming

from the floor. The calibration setup can be seen in Figure 3.3. The signal used for the

calibration process was the same exponential sweep which was used for the

measurements. The microphone was then rotated in steps of 30-40 degrees. In every

position an impulse response was recorded and the obtained data set was used for the

system’s calibration.

Figure 3.3: The setup used for obtaining the data used for calibration of the measuring system.

4 For calculating Strength, G a correction value of 14dB was added in the results in order to compensate

for the fact that the sound source was positioned 2 and not 10m away.


17

3.1.3. Procedure

Theatre of Epidauros

For the Theatre of Epidauros, 3 source and 15 receiver positions were chosen. The

symmetry of the theatre was taken into account and the receiver positions were chosen

in such a way that a grid of measuring points covering only the left half of the koilon,

was created; the conclusions that can be derived from those measurements can then be

generalized for the whole seating area. The receiver positions were always chosen to

be approximately at the center of the respective row and the microphone was

positioned at a height of around 60cm from the seat.

The kerkides were coded with letters and the rows with numbers; thus, each

measuring position is indicated by a capital letter followed by a number (eg. A25, C15

etc.). The positions can be seen on Figure 3.4.

Figure 3.4: Plan view of the Theatre of Epidauros. The receiver positions are marked with black

dots. The letters and numbers reveal the coding that was chosen for the receiver positions (eg.

A5, C15, U15 etc.).

The source positions are marked with a capital S and a number from 1 to 3 (Figure

3.5). To be more specific, source position S1 is exactly at the center of the orchestra

of the theatre (thymeli) at a height of 1,5m from the ground. The positions S2 and S3

were chosen in such a way, that they are situated at the vertices of the two equal

C

A

E

M

Q

U

5 15 25 5 15


18

angles of an isosceles triangle with its equal sides being around 14,80m and its base

being around 10m. The height of the source at positions S2 and S3 was chosen to be

3,80m; according to Vitruvius the height of the logeion in an ancient Greek theatre

“ought to be not less than ten feet or more than twelve”[6]. Thus, by positioning the

sources in this way, an effort of recreating the source positions indicated by Vitruvius

was made; of course, the absence of a skene could not be compensated. On the other

hand, source positions S2 and S3 could give us some useful information about the

acoustical behavior of the theatre in case loudspeakers are put in those positions.

Figure 3.5: Plan view of the orchestra and skene of Theatre of Epidauros. The source positions

are marked with red dots. The letters and numbers reveal the coding that was chosen for the

source positions (S1, S2 and S3).

Figure 3.6: Setting up source position S2.

S1

S2 S3

14,80m 14,80m

10m


19

Theatre of Ancient Epidauros

For the Theatre of Ancient Epidauros, 3 source and 12 receiver positions were chosen.

The symmetry of the theatre was taken into account in this case as well, and the

positions were chosen in such a way that a grid of measuring points covering the left

half of the koilon was created. The coding of the positions is based on the principal

that was chosen for the Theatre of Epidauros. The positions can be seen on Figure 3.7.

A

?

G

?

??

?

T

?

Figure 3.7: Plan view of the Theatre of Ancient Epidauros. The receiver positions are marked

with black dots. The letters and numbers reveal the coding that was chosen for the receiver

positions (eg. A2, C8, E14 etc.).

The source positions are marked with a capital S and a number from 1 to 3. In this

case, all source positions were at a height of 1,5m from the wooden construction that

was covering the ruins of the skene and the whole orchestra at the time of the

conduction of the measurements (Figure 3.8). The exact positions of the sources can

be seen on Figure 3.9. In this case as well, the source positions S2 and S3 could give

A

B

C D E

2

8

14


20

us some useful information about the acoustical behavior of the theatre in case

loudspeakers are put in those positions.

Figure 3.8: The wooden construction that was built on top of the orchestra and skene of the

Theatre of Ancient Epidauros during the time that the measurements were conducted.

?

Figure 3.9: Plan view of the orchestra and skene of Theatre of Epidauros. The source positions

are marked with red dots. The letters and numbers reveal the coding that was chosen for the

source positions (S1, S2 and S3).

6,14m

4,20m 4,20m

S1

S2 S3


21

3.2. Recordings

3.2.1. Equipment

The equipment that was used for the recordings was 3 hard disc recorders (Sound

Devices 722T and 744T) and 3 sets of binaural microphones (2 Sennheiser and 1 made

at the Department of Acoustic Technology-DTU).

Figure 3.10: The pair of “home-made”, binaural microphones that were used for the conduction

of the recordings at one of the positions.

3.2.2. Calibration

After fixing the gain controls at a specific level (different in each recorder depending

on the seating position5) a reference signal was recorded in all three hard disc

recorders. The reference signal was white noise MLS noise6 at 84dB SPL, which was

produced by the ODEON software. The sound source was the dodecahedron

loudspeaker and each one of the persons carrying the recording equipment recorded

consecutively, a short sound sample at a distance of 2m from the source and at 1,5m

from the ground. These reference sound files were later used for normalization

purposes in order to compensate for the differences in the initial gain setups. The

sound files could then be directly compared to each other.

For the manipulation of all the recorded files the Adobe Audition software was used.

5 The gain in each recorder was set to be as high as possible in order for the recorded signal to have a

high signal-to-noise ratio, but also taking care that no clipping distortion was introduced. 6A MLS (Maximum Length Sequence) is a periodic pseudo random white noise signal, having the

desirable property that its frequency spectrum over one period is as flat as the spectrum of an ideal

impulse. Many types of MLS exist. DIRAC uses a subset, with period lengths ranging from 0,34 to

23,8 seconds [7].


22

3.2.3. Procedure

One amplified and one non-amplified performance was recorded in each theatre. Parts

of the performances were recorded simultaneously in 3 different positions in each

theatre. The recording positions can be seen in Figure 3.11 and Figure 3.12.

Figure 3.11: The red circles indicate the recording positions at the Theatre of Epidauros.

The performances that were recorded in the Theatre of Epidauros were:

• “Persian” by Aeschylos

The main type of sound was speech. The performance was not amplified and the

scenography was very modest (Figure 3.13).

• “Suppliants” by Euripides

In this modern version of Euripides’s ancient tragedy, the types of sounds were

both music and speech. The performance was amplified with a particular

amplification system; apart from the array of loudspeakers hanging in either side

of the stage, 8 loudspeakers were positioned tilted on the orchestra floor, facing

the klimakes (Figure 3.13).

C

A

E

M

Q

U

5 15 25 5 15


23

A

?

G

?

??

?

T

?

Figure 3.12: The red circles indicate the recording positions at the Theatre of Ancient Epidauros.

The performances that were recorded in the Theatre of Ancient Epidauros were:

• “Eros Thilikratis”

The main type of sound was speech and the spoken parts of the performance were

not amplified.

• “Chorika”

This was an amplified musical performance with many persons (musicians,

singers) performing on the stage.

A

B

C D E

2

8

14


24

Figure 3.13: Two very different stage setups at the Theatre of Epidauros; on the left picture the

stage setup for the “Persians” and on the right picture the stage setup for the “Suppliants”.

Description of the models

25

4. Description of the models

Both theatres were modeled in ODEON v8.5. First the geometrical models were made

based on plans of the theatres, as well as on photos taken on the sites. In order to

simulate “open-air” conditions, both models were surrounded by a totally absorbing

box. Then the absorption coefficients were assigned to the surfaces by assigning

different materials, in order to achieve as close match as possible between measured

and simulated values in terms of Reverberation Time and Strength. All the materials

that were used were found in the “Global Material Library” of ODEON v.8.5. Finally,

for both theatres “Marble slabs” were used for the area of the koilon, while for the

orchestra of the Theatre of Epidauros “Glaze plaster” and for the orchestra of the

Theatre of Ancient Epidauros “Floors, Hollow wooden podium”.

The scattering coefficients were chosen according to the suggestions proposed in the

manual of ODEON; thus, very scattering, rigid surfaces that were not modeled in

detail (like the koilon of the theatres) were given a high scattering coefficient of 0,4.

For the rest of the surfaces (orchestra, stage etc.) a value of 0,05 was assigned.

The models can be seen in Figure 4.1 and Figure 4.2.

Odeon©1985-2006

Figure 4.1: The model of the Theatre of Epidauros. The surrounding box is totally absorbing, in

an effort to simulate “open-air” conditions.


26

Odeon©1985-2006

Figure 4.2: The model of the Theatre of Ancient Epidauros.


27

For examining the effect of the addition of a stage building on the acoustical behavior

of the theatres, both models were modified. In the figures that follow, the modified

models are shown. In the Figure 4.3 the dimensions of the stage buildings are given

and the models with the added stage buildings are shown in Figure 4.4 and Figure 4.5.

a [m] b [m] c [m] d [m] e [m] f [m] G [m]

Theatre of Epidauros 25,00 10,00 15,00 7,00 10,33 8,00 3,00

Theatre of Ancient

Epidauros 17,50 6,40 10,00 4,50 6,18 4,50 0,50

Figure 4.3: Rough sketches and the dimensions of the stage buildings.

a

b

c

d

e

f

g


28

Odeon©1985-2006

Figure 4.4: The model of the Theatre of Epidauros with the added stage building.

Odeon©1985-2006

Figure 4.5: The model of the Theatre of Ancient Epidauros with the added stage building.

Measurements and Simulations

29

5. Measurements and Simulations

In this chapter, the results from the acoustic measurements will be presented, as well

as data obtained from simulations in ODEON. The analysis of the data focuses on the

comparison of the following acoustic quantities:

• Sound Strength, G (in dB)

• Reverberation Time, T30 (in sec)7

• Early Decay Time, EDT (in sec)

• Clarity, C80 (in dB)

• Speech Transmission Index, STI

The detailed definitions of the quantities can be found in [8].

5.1. Theatre of Epidauros-Results and discussion

5.1.1. Comparison of source positions

In this section the results obtained from measurements with different source positions

will be discussed. The analysis will focus on the three receiver positions that were

used for the recordings (i.e. E15, C25 and U5). The reason is that by comparing those

9 source-receiver configurations (3 source and 3 receiver positions) it is expected to

reach to conclusions that can be related to the listening tests.

An important note that it is necessary to point out is that the measurements with the

source position S3 were conducted the day after the measurements with S1 and S2

were conducted. The day when the measurements with S3 were conducted the

weather conditions were quite different from the previous day; the temperature was

lower and the atmosphere was more humid. The level of the background noise was

much lower since there was no sound from cicadas (at least not until the

measurements had finished). Furthermore, another set of impulse responses meant for

creating a calibration data set (as described in 3.1.3) was obtained and used for

calibrating the system. In the following figures it is possible to see that S3 has given

results quite different from S2, especially in the values for EDT and G.

7 The reason why T30 was chosen and not T20, is explained in paragraph 9.1


30

E15_S1

E15_S2

E15_S3

U5_S1

U5_S2

U5_S3

C25_S1

C25_S2

C25_S3

-12,00

-10,00

-8,00

-6,00

-4,00

-2,00

0,00

30 35 40 45 50 55 60 65 70 75

Distance from source [m]

Strength, G [dB]

E15_S1

E15_S2

E15_S3

U5_S1

U5_S2

U5_S3

C25_S1

C25_S2

C25_S3

Figure 5.1: Strength (G) versus distance at the Theatre of Epidauros. Each point represents the

average of the values at 500Hz and 1000Hz octave bands, for the specific source-receiver setup

[8].

For the source positions S1 and S2, the Strength of sound is inversely proportional to

distance and with increasing distance strength seems to decrease with an almost

constant slope. In free-field conditions the sound pressure level drops 6dB per

doubling of distance. Due to the fact that the sound field in the space of the theatre is

not “free” at all a less steep drop would be expected. Nevertheless, by comparing

E15_S1 and U5_S1 it seems that this is not the case here.

Concerning S3, the values of G in all receiver positions are even higher than S1

(Figure 5.1); which is strange since S1 is almost 15m closer to the receiver points than

S3 (Figure 3.5). It could be argued that it is the different set of data that has been used

for calibration that creates this difference. If that was the case then particular data

would only be expected for the G values since among the quantities presented and

compared in this study, they are the only ones which are affected by the calibration of

the system.

However, some seemingly irregular results are observed in Figure 5.2 for EDT, as

well. The values obtained with the source positioned at S3 are much higher than the

ones measured for either S1 (around 0,09) or S2 (around 0,15). Unlike G, the

calculation of EDT is not affected by the calibration procedure since it is calculated


31

directly from the slope of the integrated impulse response curves. Thus, the

explanation of a calibration error does not cover this case.

E15_S1

E15_S2

E15_S3

U5_S1

U5_S2

U5_S3

C25_S3

C25_S1

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

30 35 40 45 50 55 60 65 70 75


Early Decay Tim

e, EDT [dB]

E15_S1

E15_S2

E15_S3

U5_S1

U5_S2

U5_S3

C25_S1

C25_S3

Figure 5.2: Early Decay Time (EDT) versus distance at the Theatre of Epidauros. Each point


receiver setup [8].

An alternate explanation could attribute these results to the effect of the weather

conditions on the acoustic properties of the theatre. Taking into account that the

measurements were conducted early in the morning under the conditions described

previously, it could be possible that the temperature gradient in the different layers of

air was such that could cause a “downward” bending of the sound rays. This is a

complicated phenomenon and its explanation is out of the scope of this investigation

but the occurrence of this phenomenon would mean that a bigger amount of sound

rays (comparing to the previous day) would reach the receiver positions. This could

explain the higher G values but also the higher EDT values. Nevertheless, this

assumption cannot be proven from the analysis undergone so far; in previous

investigations of this phenomenon at the Theatre of Epidauros no pronounced effect

on the acoustical properties of the theatre had been observed [9].


32

E15_S1E15_S2

E15_S3 U5_S1

C25_S1

C25_S3U5_S2 U5_S3

C25_S2

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

30 35 40 45 50 55 60 65 70


STI

E15_S1

E15_S2

E15_S3

U5_S1

U5_S2

U5_S3

C25_S1

C25_S2

C25_S3

Figure 5.3: Speech Transmission Index (STI) versus distance at the Theatre of Epidauros. Each

point represents the average of the values at 500Hz and 1000Hz octave bands, for the specific

source-receiver setup [8].

A safe observation that it is possible to point out is that STI (as shown in Figure 5.3)

is not affected by the source position and it is over 0,7 for every source-receiver

configuration. This observation justifies the fame of this theatre that a performance is

intelligible even at the most remote seats.

As far as Reverberation time is concerned, looking at Figure 5.4 it is possible to see

that there is no obvious dependency of T30 from the source-receiver distance.

Furthermore in Figure 5.5 it is shown that when the source is positioned on the

orchestra the values of T30 are higher comparing to the other source positions. This

could be explained by the fact that in the absence of a skene, when the source is

positioned in the back (where the skene used to be), more sound rays “escape” from

the space of the theatre. In Figure 5.5 the value that T30 takes at 4000Hz for S3 can

be seen. As said before, the day that measurements with source position S3 were

conducted was the only day where there was no background noise from cicadas; thus

it was possible to obtain reliable results for T30 at this octave band.


33

E15_S1

U5_S1

U5_S2

U5_S3

C25_S3

E15_S2

E15_S3

C25_S1

C25_S2

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

30 35 40 45 50 55 60 65 70 75


Reverberation Tim

e, T30 [sec]

E15_S1

E15_S2

E15_S3

U5_S1

U5_S2

U5_S3

C25_S1

C25_S2

C25_S3

Figure 5.4: Reverberation Time (T30) versus distance at the Theatre of Epidauros. Each point


receiver setup [8].

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

100 1000 10000

Frequency [Hz]

Reverberation Tim

e, T30 [sec]

S1

S2

S3

Figure 5.5: Reverberation Time (T30) versus frequency at the Theatre of Epidauros. Each point

represents the average of the values measured in all receiver positions, for the specific octave

band. The different colors indicate the position of the sound source; blue, pink, green correspond

S1, S2 and S3, respectively.


34

The source positions S2 and S3 were chosen to be placed at the positions where

(according to Vitruvius) the actors were performing in the ancient times. It was

attempted to investigate whether by positioning the sound sources at the specific

positions would have a positive effect in the acoustical behavior of the theatre. Under

the present conditions of the theatre (absence of skene) this does not seem to be the

case. According to our data the source position does not affect the acoustical

properties of the Theatre of Epidauros, except from an increase in T30 values when

the source is positioned on the orchestra. However, this could be an improvement for

performing music (since T30 is already too low for musical performance) but as far as

speech is concerned any source position would be just as good in terms of

intelligibility.

Last but not least, taking into consideration the results obtained from source position

S3 it is clear that outdoor measurements depend on factors that apart from the fact that

they are frequently impossible to either predict or control, their effects are difficult to

be investigated.


35

5.1.2. Evaluation of the model

Based on the previous analysis on the effect of source positions it was decided to

position the source on the orchestra, in the model of the Theatre of Epidauros. Thus,

in the analysis that follows the measured data that were obtained from this specific

source position will be presented and compared with the simulated results.

In order to evaluate the model, the receiver positions were chosen to be the same as in

the measurements. In the following graphs, it possible to compare the values given by

the ODEON model and the values obtained by the measurements.

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

100 1000 10000

Frequency [Hz]

Reverberation Tim

e, T30 [sec]

Figure 5.6: Reverberation Time (T30) versus frequency at the Theatre of Epidauros. The source

is positioned in the center of the orchestra. Each point represents the average of the values


the measured and simulated values, respectively.

According to the measurements, the Reverberation time of the theatre is around 1,3

seconds in all frequencies from 125Hz to 2000kHz. Background noise from cicadas

affected the measurements at 4000kHz, giving extremely high values (around 5-6 sec)

at this specific frequency band. Thus, those values where omitted from the presented

results.

The results from the model are in accordance to the ones of the measurements

especially in the frequency range from 500 to 2000Hz.


36

-20

-15

-10

-5

0

5

100 1000 10000

Frequency [Hz]

Strength, G [dB]

C5_measured C5_simulated C25_measured

C25_simulated Q15_measured Q15_simulated

Figure 5.7: Strength (G) versus frequency for 3 different receiver positions at the Theatre of

Epidauros. The source is located in the center of the orchestra. The solid and dotted lines indicate

measured and simulated values, respectively.

In Figure 5.7 it possible to observe that the measured values for G at the 125Hz

octave band drop as the receiver moves to the upper rows. This could be due to the

fact that the phase shift between the direct sound and the orchestra floor reflections is

such that they interfere destructively when reaching the receiver positions. The sound

pressure level at those points (in the specific octave band) takes lower values than it

does in the other octave bands. A more detailed explanation of this phenomenon is

given in section 9.2 of the Appendix.

Above 500Hz, strength does not seem to depend strongly on frequency. According to

the measurements, in this frequency interval, strength is almost constant for a specific

receiver position. The values obtained from the simulation -with the exception of the

row which is closer to the source- are in general lower in the same interval. It is

possible to see that for C25 the computer simulation results and the measured data are

in quite good agreement.


37

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Reverberation Tim

e, T30 [sec]

Figure 5.8: Reverberation Time (T30) versus distance at the Theatre of Epidauros. The source is

positioned in the center of the orchestra. Each point represents the average of the values at


indicate the measured and simulated values, respectively.

In Figure 5.8 it can be seen that, according to the measurements, Reverberation

Time (T30) ranges from 0,97 to 1,54 seconds. It can also be seen that as the distance

from the source increases, the dispersion of the T30 values becomes smaller; T30 in

the most remote positions is around 1,35 seconds.

The model gives values of T30 which have a larger dispersion, ranging from 0,62 to

1,67 seconds.


38

-14,00

-12,00

-10,00

-8,00

-6,00

-4,00

-2,00

0,00

2,00

4,00

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Strength, G [dB]

Figure 5.9: Strength (G) versus distance at the Theatre of Epidauros. The source is positioned in



and simulated values, respectively.

The Strength according to the measurements drops from 1,30dB for the places close

to the source to -8,21dB for the most remote ones. The results from the model indicate

a similar behavior, with the Sound Pressure Level decreasing from 2,9 to -12,15dB.


39

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Early Decay Tim

e, EDT [sec]

Figure 5.10: Early Decay Time (EDT) versus distance at the Theatre of Epidauros. The source is




Early Decay Time decreases with increasing distance from 0,26 seconds at the

positions which are closer to the source to 0,05 seconds for the positions which are

further away. The values obtained from the simulation follow a similar pattern,

ranging from 0,14 to 0,04 seconds.

It is easy to identify 5 points on Figure 5.10 where EDT takes very high values. This

particularity of the theatre is also verified by the model. Those points correspond to

receiver positions situated on the first kerkida and more specifically to the positions

A5, A15, A25, M5 and M15. The explanation of this phenomenon is that the specific

positions receive quite strong reflections coming from the seating area opposite to

them.

In Figure 5.11 and Figure 5.12, it is possible to compare the decay curves between the

positions A25 and C25, which are positioned in the same row but different kerkida.


40

E, SimulatedgfedcbE, IntegratedgfedcbE, CorrectedgfedcI, SimulatedgfedcI, Integratedgfedc

Decay curves at 1000 Hz, T30=1,15 (s)

Time (seconds rel. direct sound)

10,950,90,850,80,750,70,650,60,550,50,450,40,350,30,250,20,150,10,050

SPL (dB)

-5

-10

-15

-20

-25

-30

-35

-40

-45

-50

-55

-60

-65

Odeon©1985-2006

Figure 5.11: The simulated and integrated decay curves at 1000Hz produced by ODEON, for

position A25.

E, SimulatedgfedcbE, IntegratedgfedcbE, CorrectedgfedcI, SimulatedgfedcI, Integratedgfedc

Decay curves at 1000 Hz, T30=1,52 (s)

Time (seconds rel. direct sound)

1,110,90,80,70,60,50,40,30,20,10

SPL (dB)

-10

-15

-20

-25

-30

-35

-40

-45

-50

-55

-60

-65

Odeon©1985-2006

Figure 5.12: The simulated and integrated decay curves at 1000Hz produced by ODEON, for

position C25.

For this example, it is possible to see that in position A25 the SPL of the direct sound

decreases until 113msec where an increase of SPL is observed. This is not observed in

position C25. This fact indicates that A25 receives strong reflections from a surface

being about 39 meters away (Figure 5.13).


41

P1

9

P1

Surface: 1531

Path <m>: 38,93

Time <ms>: 113Odeon©1985-2006

Figure 5.13: The direction of reflections responsible for the increase of the energy at 113msec at

position A25, according to ODEON.

Due to the fact that these reflections are relatively loud (comparing to the direct

sound) and arrive rather late after the direct sound, they will be perceived as distinct

echo [10]; however, it must be stressed that the measurements were made when the

theatre was unoccupied. In the case of the occupied theatre the absorption added by

the audience would effectively reduce the amount of energy reflected to those

positions.


42

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

18,00

20,00

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Clarity, C80 [dB]

Figure 5.14: Clarity (C80) versus distance at the Theatre of Epidauros. The source is positioned


1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots indicate the

measured and simulated values, respectively.

As it can be seen in Figure 5.14, in the same 5 positions discussed before, Clarity

takes low values; this result was expected since Clarity is an early-to-late arriving

sound energy ratio and there are more late-arriving reflections in those positions. In

general, Clarity is high and even at the seats which are further away from the source it

is more than 14dB. [8]


43

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


STI

Figure 5.15: Speech Transmission Index (STI) versus distance at the Theatre of Epidauros. The




Finally, the values of the Speech Transmission Index are in all positions higher than

0,68 according to the measurements. The simulation gives in general very high values

for STI (more than 0,9), while the receiver positions situated in the first kerkida can

be identified at the points where the values of STI are around 0,7. However, it should

be mentioned that during the ODEON calculations the background noise was not

defined. Therefore, ODEON results for STI represent an ideal situation, where there is

no background noise at all.

The calibration of the model and the good match between measured and simulated

values gives the opportunity to use the computer model to check the impact of the

addition of the stage to the acoustic properties of the theatre.


44

5.1.3. Addition of a stage

The effect of the construction of a simple stage on the acoustic properties of the

Theatre of Epidauros will be discussed here.

As shown on Figure 5.16, the addition of the stage building does not affect much T30.

It could be said that it reduces the dispersion of the values around a mean value of

around 1,4 seconds, while Strength is increased in most positions by 1-2dB (Figure

5.17). Early Decay Time increases in all positions and the increase is more obvious as

the receiver moves towards the positions which are further away from the source

(Figure 5.18). As expected, the increase of EDT is followed by a drop of Clarity in

most positions by more than 7dB (Figure 5.19). According to these last two figures, it

could be stated that the echo phenomenon appearing in the first kerkida (discussed

previously) seems to be smoothened. Moreover, STI remains between 0,6 and 0,7

even for the most remote positions (Figure 5.20). This result was expected since STI

depends on reverberation time and background noise; background noise is not taken

into account and T30 does not change too much, so STI should be at the same levels

as before.

0,00

0,50

1,00

1,50

2,00

2,50

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Reverberation Tim

e, T30 [sec]

wo/ stage

w/ stage

Figure 5.16: Reverberation Time (T30) versus distance at the Theatre of Epidauros. The source is



indicate values obtained from the model of the theatre with and without stage, respectively.


45

-14,00

-12,00

-10,00

-8,00

-6,00

-4,00

-2,00

0,00

2,00

4,00

6,00

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Strength, G [dB]

wo/ stage

w/ stage

Figure 5.17: Strength (G) versus distance at the Theatre of Epidauros. The source is positioned in



obtained from the model of the theatre with and without stage, respectively.

0,00

0,50

1,00

1,50

2,00

2,50

3,00

3,50

4,00

4,50

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Early Decay Tim

e, EDT [sec]

wo/ stage

w/ stage

Figure 5.18: Early Decay Time (EDT) versus distance at the Theatre of Epidauros. The source is





46

-5,00

0,00

5,00

10,00

15,00

20,00

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Clarity, C80 [dB]

wo/ stage

w/ stage

Figure 5.19: Clarity (C80) versus distance at the Theatre of Epidauros. The source is positioned


1000Hz octave bands, for the specific receiver position [8]. The pink and blue dots indicate values

obtained from the model of the theatre with and without stage, respectively.

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00


Speech Transmission Index, STI

wo/ stage

w/ stage

Figure 5.20: Speech Transmission Index (STI) versus distance at the Theatre of Epidauros. The





47

Summarizing, by adding the stage building it is possible to compliment the

reverberance of the theatre but not without paying the price of the sound becoming

less clear. Thus, judging only from the above presented parameters, a musical

performance could benefit more from the presence of a stage building, than a

performance were the dominant type of sound is speech.

Graphical illustrations of the effect of the addition of a stage at the Theatre of

Epidauros can be found in section 9.3 of the Appendix.


48

5.2. Theatre of Ancient Epidauros-Results and discussion

5.2.1. Comparison of source positions

Similar to the case of the Theatre of Epidauros, in this section the results obtained

from measurements with different source positions will be discussed. Since it was not

possible to obtain recordings at the exact measured receiver positions, data obtained

from the positions which are the closest to the recording positions will be examined

(i.e. C2, C8, C14 and D8). Taking into consideration the much smaller size of the

Theatre of Ancient Epidauros this approximation is not expected to introduce an error

when comparing acoustic quantities like T30, G, EDT and STI. The expectation of

reaching to conclusions that could be related to the listening tests dictated the choice

of the specific 12 source-receiver configurations (3 source and 4 receiver positions).

In the case of this theatre all measurements were conducted during the same day and

only one data set was used for the calibration of the measuring system. Thus an error

in the calibration cannot explain the fact that when the source is positioned at S3

Strength at the receiver points is, in general, higher than Strength measured for the

other configurations with almost the same distance between source and receiver

(Figure 5.21).

C2_S1

C2_S2

C8_S2 C8_S3

D8_S1

D8_S3

C14_S2

C14_S3

C2_S3

C8_S1

D8_S2

C14_S1

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,00

15 20 25 30 35


Strength, G [dB]

C2_S1

C2_S2

C2_S3

C8_S1

C8_S2

C8_S3

D8_S1

D8_S2

D8_S3

C14_S1

C14_S2

C14_S3

Figure 5.21: Strength (G) versus distance at the Theatre of Ancient Epidauros. Each point


receiver setup [8].


49

The “downward” bending of sound rays cannot be responsible for this result either,

because the S3 was measured in the middle of the day when the gradient of

temperature in the air layers would cause the opposite phenomenon (i.e. “upward”

bending of sound rays), thus lower G values would be expected. So far, no satisfying

explanation for this result can be given about this fact.

However, judging by the results obtained from the source positions S1 and S2 it is

possible to see that in general G depends rather on the distance from the source, than

the specific source position. Similar to the case of the Theatre of Epidauros, G seems

to drop more than 6dB per doubling of distance which would be the case in free-field

conditions (C2_S1 and C14_S1).

C2_S2

C2_S3

C8_S1

C8_S2

D8_S1

D8_S2

D8_S3

C14_S1

C14_S2

C14_S3

C2_S1

C8_S3

0,00

0,10

0,20

0,30

0,40

0,50

0,60

15 20 25 30 35


Early Decay Tim

e, EDT [sec] C2_S1

C2_S2

C2_S3

C8_S1

C8_S2

C8_S3

D8_S1

D8_S2

D8_S3

C14_S1

C14_S2

C14_S3

Figure 5.22: Early Decay Time (EDT) versus distance at the Theatre of Ancient Epidauros. Each

point represents the average of the values at 500Hz and 1000Hz octave bands, for the specific

source-receiver setup [8].

Concerning, Early Decay Time (shown in Figure 5.22) source position S3 in general

seems to give the lowest results, while for S1 and S2 the values are around 0,3 (with

the exception of D8_S1 and D8_S2).


50

C2_S1C2_S2

C8_S2

C8_S3

D8_S2

C14_S1

C14_S3

C2_S3

C8_S1

D8_S1D8_S3

C14_S2

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

15 20 25 30 35


STI

C2_S1

C2_S2

C2_S3

C8_S1

C8_S2

C8_S3

D8_S1

D8_S2

D8_S3

C14_S1

C14_S2

C14_S3

Figure 5.23: Speech Transmission Index (STI) versus distance at the Theatre of Ancient

Epidauros. Each point represents the average of the values at 500Hz and 1000Hz octave bands,

for the specific source-receiver setup [8].

Speech intelligibility in the Theatre of Ancient Epidauros is very high (Figure 5.23)

and independent both from source-receiver distance and source position. This result

was expected since the background noise was constant during the measurements and

furthermore (as it can be seen in Figure 5.24 and Figure 5.25) reverberation time is

nearly independent of either source-receiver distance or frequency.


51

C2_S1

C8_S1C8_S2

C8_S3

D8_S1

D8_S2D8_S3

C14_S1

C14_S2

C14_S3

C2_S2

C2_S3

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

15 20 25 30 35


Reverberation Tim

e, T30 [sec]

C2_S1

C2_S2

C2_S3

C8_S1

C8_S2

C8_S3

D8_S1

D8_S2

D8_S3

C14_S1

C14_S2

C14_S3

Figure 5.24: Reverberation Time (T30) versus distance at the Theatre of Ancient Epidauros.


specific source-receiver setup [8].

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

100 1000 10000

Frequency [Hz]

Reverberation tim

e, T30 [sec]

S1

S2

S3

Figure 5.25: Reverberation Time (T30) versus frequency at the Theatre of Ancient Epidauros.

Each point represents the average of the values measured in all receiver positions, for the specific

octave band. The different colors indicate the position of the sound source; blue, pink, green

correspond S1, S2 and S3, respectively.


52

In this section it was attempted to investigate whether the source position could have

an effect in the acoustical behavior of the Theatre of Ancient Epidauros. Under the

present conditions of the theatre (absence of skene) this does not seem to be the case.

The Theatre of Ancient Epidauros is “dry”, in terms of reverberance, and taking into

account that both Strength and STI are high in all receiver positions, it is (in its

present conditions) more suitable for performances where the main type of sound is

speech.


53

5.2.2. Evaluation of the model

For evaluating the model of the Theatre of Ancient Epidauros, the source under

consideration is the one located on the orchestra and the receiver positions were

chosen to be the same as in the measurements. In the following graphs, it possible to

compare the values given by the ODEON model and the values obtained by the

measurements.

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

100 1000 10000

Frequency [Hz]

Reverberation Tim

e, T30 [sec]

Figure 5.26: Reverberation Time (T30) versus frequency at the Theatre of Ancient Epidauros.

The source is positioned in the center of the orchestra. Each point represents the average of the

values measured in all receiver positions, for the specific octave band. The pink and blue line,


In Figure 5.26 it is possible to see that the Reverberation Time (T30) is quite flat in

the frequency spectrum from 500 to 2000Hz, as indicated by both the measured and

the simulated values. Nevertheless, the simulated values are around 0,1 second lower

in most frequency bands. It is important to mention that the results of the

measurements at 4000Hz were omitted in this case as well; the increased background

noise floor at this frequency band created by cicadas made it impossible to conduct a

reliable measurement.


54

-2

0

2

4

6

8

10

12

100 1000 10000

Frequency [Hz]

Strength, G [dB]

D2_measured D2_simulated D14_measured D14_simulated

Figure 5.27: Strength (G) versus frequency at the Theatre of Ancient Epidauros. The source is

positioned in the center of the orchestra. The solid and dotted lines indicate the measured and

simulated values, respectively.

According to the measurements, the Theatre of Ancient Epidauros has a particular

acoustical behavior in terms of Strength (G). Apart from the fact that it is possible to

observe an attenuation of the sound pressure level with increasing frequency (starting

from 250Hz), a dip is observed at the 1000Hz octave band. This could be related to

the so-called seat-dip effect, where in some concert halls similar dips are observed,

which depend on the distance between the rows of seats and the height of the seats.

However, in this case it is not possible to make a secure assumption for this

phenomenon.

Similar to the Theatre of Epidauros, a strong attenuation of the lower frequencies is

observed. In this case as well, probably the phase shift between the direct sound and

the floor reflections is such that they interfere destructively when reaching the

receiver positions; thus the sound pressure level at these point (in the specific octave

band) takes lower values than it does in the other octave bands. A more detailed

explanation of the phenomenon can be found in section 9.2.


55

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Reverberation Tim

e, T30 [sec]

Figure 5.28: Reverberation Time (T30) versus distance at the Theatre of Ancient Epidauros. The




Figure 5.28 shows that the model calculated, in general, lower values (around 0,45

seconds) for the Reverberation Time (T30) comparing to the measurements (around

0,55 seconds). However, in both the simulated and the real theatre, Reverberation

Time (T30) does not depend on the distance from the source. This is, most likely,

related to the size of the theatre and by looking at Figure 5.8 it is possible to see that

in the case of the much larger Theatre of Epidauros, T30 is more affected by the

distance from the source.

In terms of Strength (G), the model estimated values of approximately 2dB lower

than the real data. It must be noted though that the slope of the decrease of the

strength with increasing distance is similar in the real and the virtual theatre (Figure

5.29).

Concerning Early Decay Time (EDT) it is possible to observe a large dispersion of

the values for both the simulated and measured values. By looking at this graph it is

not possible to identify the pattern that the values of Early Decay Time follow.

On the other hand, it is interesting to observe the results plotted versus the specific

kerkida that the receiver positions are situated (Figure 5.31).


56

-2,00

0,00

2,00

4,00

6,00

8,00

10,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Strength, G [dB]

Figure 5.29: Strength (G) versus distance at the Theatre of Ancient Epidauros. The source is




0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Early Decay Tim

e, EDT [sec]

Figure 5.30: Early Decay Time (EDT) versus distance at the Theatre of Ancient Epidauros. The





57

In Figure 5.31 it is possible to observe that according to the measurements Early

Decay Time increases as we approach to the axis of symmetry of the theatre (kerkida

E). In the kerkides D and E Early Decay Time ranges from 0,44 to 0,51 seconds

depending on the row. It seems that for some reason there is a focusing of reflections

towards kerkida E. This phenomenon is probably due to the reflections coming from

the wooden panel that is shown in Figure 5.32. This panel was installed on a wooden

platform which was built on the ruins of the skene, perpendicular to the theatre’s axis

of symmetry at the time that the measurements took place.

Nevertheless, it must be stated that even though this panel was included in the

ODEON model the results did not show a similar behavior Figure 5.33.

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0 1 2 3 4 5 6Number of Kerkida

Early Decay Tim

e, EDT [sec]

Row2 measured

Row8 measured

Row14 measured

Figure 5.31: Early Decay Time (EDT) versus the number of the kerkida at the Theatre of Ancient


the orchestra. Each point represents the average of the values at 500Hz and 1000Hz octave

bands, for the specific receiver position [8]. All points indicate measured values.


58

Figure 5.32: View of the Theatre of Ancient Epidauros at the time of the measurements.

0,00

0,10

0,20

0,30

0,40

0,50

0,60


Early Decay Tim

e, EDT [sec]

Row2 measured

Row8 measured

Row14 measured

Row2 simulated

Row8 simulated

Row14 simulated

Figure 5.33: Early Decay Time (EDT) versus the number of the kerkida at the Theatre of Ancient


the orchestra. Each point represents the average of the values at 500Hz and 1000Hz octave

bands, for the specific receiver position [8]. The solid and dotted lines indicate the measured and



59

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

18,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Clarity, C80 [dB]

Figure 5.34: Clarity (C80) versus distance at the Theatre of Ancient Epidauros. The source is




In terms of Clarity (C80) the measured values range from 12,40 to 16,39 dB, while

the simulation gave values from 8,75 to 13,20 dB (Figure 5.34). According to the

model, Clarity seems to increase with increasing distance, although this phenomenon

is not observed in the measurements. The trend that it is possible to observe in the

measured data is that the dispersion of the results reduces as the receiver is further

away from the source.


60

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

18,00


Clarity, C80 [dB]

Row2 measured

Row8 measured

Row14 measured

Row2 simulated

Row8 simulated

Row14 simulated

Figure 5.35: Clarity (C80) versus the number of the kerkida at the Theatre of Ancient Epidauros

(1 to 5 corresponds from A to E respectively). The source is positioned in the center of the

orchestra. Each point represents the average of the values at 500Hz and 1000Hz octave bands,

for the specific receiver position [8]. The solid and dotted lines indicate the measured and


By plotting C80 versus the kerkida that the receiver is positioned, it is possible to see

that Clarity seems to take its lower values, when approaching the central kerkida E

(no. 5). This phenomenon was expected since Early Decay Time shows an opposite

behavior as seen in Figure 5.31.

However, this is not observed in the simulated values, which follow a trend that

basically verifies the observation made in the previous paragraph; there is a

dependency between C80 and the row that the receiver is seating; Clarity tends to be

higher in the upper rows.


61

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00


STI


Epidauros. The source is positioned in the center of the orchestra. Each point represents the

average of the values at 500Hz and 1000Hz octave bands, for the specific receiver position [8].

The pink and blue dots indicate the measured and simulated values, respectively.

According to the measurements, the Speech Transmission Index is in general higher

than 0,65 and the positions which are closer to the source show the highest values

(around 0,80). On the other hand, according to the simulations the values of STI are

higher than the measured data, although the difference reduces when approaching the

source. This can be explained by the fact that -as in the case of the Theatre of

Epidauros- ODEON does not take into account background noise, if not defined by

the user. Thus, the simulation gives higher values for STI. The fact that STI decreases

with increasing distance in the real data reflects the fact that not only the receiver is

moving away from the source, but is also approaching the source of the background

noise, which in this case is mainly cicadas on the surrounding pine trees.

In the case of the Theatre of Ancient Epidauros the match between measured and

simulated values was not as good as in the case of the Theatre of Epidauros. The

reason is mainly the difficulty of defining the absorption and diffusion characteristics

of the materials used in the model. Nevertheless, keeping in mind its limitations it will

be attempted to use the model for examining the effects of the addition of a stage to

the acoustical behavior of the theatre.


62

5.2.3. Addition of a stage

The effect of the addition of a stage building on the acoustic parameters of the Theatre

of Ancient Epidauros is similar to the case of the Theatre of Epidauros.

Looking at Figure 5.37 it is possible to see that the addition of a stage building

increases the Reverberation Time (T30) by almost 0,2 seconds in most of the

positions, while the values for Strength (G) are increased around 2dB Figure 5.38.

In terms of Early Decay Time (EDT), Figure 5.39 indicates that the addition of the

stage has drastic effects; EDT increases in general and as the receiver moves away

from the source this increase becomes larger, exceeding 100% in the back rows of the

theatre. As expected, Clarity (Figure 5.40) is decreasing and at the most remote seats

it drops more than 6dB. However, also in the case of this theatre STI remains at levels

between 0,66 and 0,72 which signifies “Good” intelligibility (Figure 5.41).

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Reverberation Tim

e, T30 [sec]

wo/ stage

w/ stage

Figure 5.37: Reverberation Time (T30) versus distance at the Theatre of Ancient Epidauros. The





63

-1,00

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Strength, G [dB]

wo/ stage

w/ stage

Figure 5.38: Strength (G) versus distance at the Theatre of Ancient Epidauros. The source is




0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Early Decay Tim

e, EDT [sec]

wo/ stage

w/ stage

Figure 5.39: Early Decay Time (EDT) versus distance at the Theatre of Ancient Epidauros. The





64

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Clarity, C80 [dB]

wo/ stage

w/ stage

Figure 5.40: Clarity (C80) versus distance at the Theatre of Ancient Epidauros. The source is




0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00


Speech Transmission Index, STI

wo/ stage

w/ stage


Epidauros. The source is positioned in the center of the orchestra. Each point represents the

average of the values at 500Hz and 1000Hz octave bands, for the specific receiver position [8].

The pink and blue dots indicate values obtained from the model of the theatre with and without

stage, respectively.


65

From the results presented in this section it seems that the addition of a stage will

have more evident effects to the Theatre of Ancient Epidauros than in the case of the

Theatre of Epidauros. However, taking into account that T30 and EDT are quite low

even after adding the stage, the theatre is still too “dry” for hosting a non amplified

musical performance.

Graphical illustrations of the effect of the addition of a stage at the Theatre of Ancient

Epidauros can be found in section 9.4 of the Appendix.

Listening Tests

66

6. Listening Tests

A series of listening tests consisting of 2 sections was conducted in an attempt to

indirectly investigate the effect of the loudspeaker systems, which were used in some

of the performances, on subjective aspects of the acoustical character of the theatres.

The observations were related with objectively measured acoustical quantities

whenever it was possible.

In the first section the test subjects were asked to listen to 3 audio tracks recorded at

the same time in 3 different seating positions at each theatre; the task was to choose

among those 3 positions, the one that seemed closer to the source for them and also to

state the one that they would prefer to be seating.

In the second section, the test subjects were asked to choose between 2 short

presentations of different performances, which one was more intimate for them, as

well as to indicate in which of the 2 audio tracks the theatre seemed larger to them.

The test group consisted of 11 persons with ages between 20 and 30 years old. All test

subjects at the time of the tests, were working or studying at the Acoustic Technology

Department of the Technical University of Denmark. All of them had undergone

various kinds of listening tests, as well as several audiometric analyses in the past;

thus, there was no training previous to the listening tests. All test subjects had normal

hearing at mid-frequencies.

The test subjects had to give their answers on a paper form that was presented to them

at the beginning of the listening tests.

Listening Tests

67

6.1. Results and discussion

6.1.1. Section 1

Theatre of Epidauros

General information related to the performance and the presentation of the recording

positions at the Theatre of Epidauros is shown in Table 6.1 and Figure 6.1,

respectively.

LOCATION Theatre of Epidauros Theatre of Ancient Epidauros

PERFORMANCE Perses Iketides Eros Thilikratis Chorika

AMPLIFICATION No Yes No Yes

Table 6.1: General information for the performances

Figure 6.1: The recording positions at the Theatre of Epidauros. The red characters indicate the

code letters of the positions chosen for the purpose of the listening tests. The black characters

indicate the exact position; the letter corresponds to the kerkida and the number to the row. The

recording position was chosen to be approximately in the middle of the respective row.

C

C25

A

E15

B

U5

Listening Tests

68

In Figure 6.2 and Figure 6.3 it is possible to see that in both performances the test

subjects could identify that position B was the furthest. In the case of the non

amplified performance (Figure 6.2) it would be expected that the test subjects could

identify that position A was closer to the source; according to the measurements

presented in 5.1.1, Strength in A is almost 3dB higher than in B, when the source is

positioned on the orchestra (which was actually the case in this performance). The

Just Noticeable Difference according to the ISO standards [8] for Strength is 1dB, so

this result is probably affected by the fact that the microphones used at position A

introduced noise to the recordings.

For the amplified performance (Figure 6.3) it is easier to explain why most test

subjects chose seat C to be the closest to the sound source since this position was

closer to one out of the two columns of loudspeakers used in the performance.

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

A B C NO PREF.

Answers

Percentage of test subjects

Which seat seems closer to the source? Where would you prefer to seat?

Figure 6.2: The percentage of the test subjects versus their answers. The performance was not

amplified and it took place at the Theatre of Epidauros.

Listening Tests

69

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

A B C NO PREF.

Answers



Figure 6.3: The percentage of the test subjects versus their answers. The performance was

amplified and it took place at the Theatre of Epidauros.

In any case, from both figures presented above, it is clear that in both performances

the test subjects’ preference of seat is based on the perceived level of the sound

source. This conclusion was verified also by the test subjects when asked to explain

the reason or their choice. There was also a part of the test group that chose seat B for

the amplified performance for the reason that they “perceived a better balance of the

sound sources”, according to their later comments.

Listening Tests

70

Theatre of Ancient Epidauros

The recording positions chosen for the Theater of Ancient Epidauros can be seen in

Figure 6.4.

A

?

G

?

??

?

T

?

Figure 6.4: The recording positions at the Theatre of Epidauros. The red characters indicate the

code letters of the positions chosen for the purpose of the listening tests. The black characters

indicate the exact position; the letter corresponds to the kerkida and the number to the row. The

recording position was chosen to be approximately in the middle of the respective row.

At the Theatre of Ancient Epidauros it was more difficult for the test subjects to

indicate the position that was closest to the source in both amplified and non-

amplified performances. This could be explained by the fact that the difference in the

distance from the source, between the positions A, B and C was not more than a few

meters. Furthermore, by examining the measured positions C8_S1 and D8_S1, which

are close to the recording positions, according to the results presented in Figure 5.21,

G is around 5dB in both cases; however, this observation could only be related with

the non amplified performance.

C

C10

B

D6

A

C5

Listening Tests

71

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

A B C NO PREF.

Answers



Figure 6.5: The percentage of the test subjects versus their answers. The performance was not

amplified and it took place at the Theatre of Ancient Epidauros.

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

A B C NO PREF.

Answers



Figure 6.6: The percentage of the test subjects versus their answers. The performance was

amplified and it took place at the Theatre of Ancient Epidauros.

The fact that the test subjects cannot identify the seat closest to the source is also

reflected in the fact that their seat preference for the non-amplified performance

(Figure 6.5) does not follow any trend; although it must be pointed out in this case as

Listening Tests

72

well, the problematic microphones of the person recording at position A could the

reason why this position was not preferred by any test subject.

For the amplified performance though (Figure 6.6), the seat that is closer to the axis of

symmetry of the theatre seems to be preferred, for the reason of more equal balance of

the sound sources, as in the case of the large theatre.

Listening Tests

73

6.1.2. Section 2

The results and discussions on the second section of the listening tests, where the test

subjects had to indicate the performance that was more “intimate” for them, as well as

to indicate which theatre seems larger for them are presented in the following

paragraphs.

When choosing which recording would be used for this part of the listening tests there

were a number of factors to consider; first the recorded signal had to have a high

signal-to-noise ratio, thus recordings from position A were excluded. Furthermore,

Position B at the Theatre of Epidauros was too far to be compared to any of the

recordings in the Theatre of Ancient Epidauros. Eventually, the recordings from

position C in both theatres were used for this part of the listening tests.

As it can be seen in Table 6.2 when an amplified (light orange) and a non-amplified

(light yellow) performance were presented to the test subjects, they would indicate the

amplified performance as more “intimate”. Taking into account that in the amplified

performances the level of the sound was much higher than in the non amplified ones,

apparently the intimacy criterion that this test group of people had was strongly

related to the level of the sound8. It also has to be stated that a small part of the test

group noted that a female voice is always more intimate for them than a male one,

which is worth to report as a note but does not change the initial remark that intimacy

is related with the level of the source ( at least for this test group).

Another interesting observation is that when the test subjects’ had to comment on the

size of the theatres by listening to an amplified and a non-amplified performance, they

-in all cases- indicated the one where the non-amplified performance was taking place

to be bigger. This fact might imply that the presence of a sound amplification system

alters the sound field in a great extent by effectively defining the auditory space; but

of course, it could also be that again the perception of level is the cue that people tend

to follow.

8 It was considered to try to relate the results of the listening tests with objective parameters that are

more known to be related to “Intimacy” like the Late Lateral Sound Level (LG, in dB). Due to the fact

that no measurements during the performances were conducted and also because LG cannot be

obtained directly from DIRAC but indirectly from ODEON, it was decided to focus on Strength and/or

Reverberance.

Listening Tests

74

Pair 1 Large / Non Amplified Large / Amplified No difference

Which is more "intimate" for you? 9,1% 81,8% 9,1%

Which theatre seems larger to you? 90,9% 9,1% 0,0%

Pair 2 Small / Non Amplified Small / Amplified No difference



Pair 3 Small / Non Amplified Large / Amplified No difference



Pair 4 Large / Non Amplified Small / Amplified No difference



Pair 5 Large / Non Amplified Small / Non Amplified No difference



Pair 6 Large / Amplified Small / Amplified No difference



Table 6.2: Pairs that were compared in Section 2 of the listening tests. The colors stress whether

the performance was amplified (light orange) or not (light yellow). Large = Theatre of Epidauros,

Small = Theatre of Ancient Epidauros.

From the comparison of the last two pairs (Pair 5 and 6) it possible to see that the

majority of the test subjects chose in both cases the performances at the Theatre of

Ancient Epidauros to be more intimate. As said before, this could be related to the fact

that the perceived level at the Theatre of Ancient Epidauros is higher.

However, by taking a closer look at the results given for Pair 5 and by comparing the

measured quantities at those positions (Table 6.3) it can be seen that “Intimacy”

cannot be related only to perceived level; if that was the case, the 9dB difference in

strength between the 2 recording positions would most probably be sufficient to

provide a very strong cue on “Intimacy” for the non amplified performance, which is

not the case as shown in Table 6.2.

Furthermore, looking at the same pair it can be seen that the test subjects’ could not

definitely decide on the size of the theatre. In Table 6.3 it is possible to see that the

acoustic quantities at the 2 positions have large differences. Nevertheless, this could

be explained by the fact that the criterion on how to evaluate the pairs had been

Listening Tests

75

defined by the previous paired comparisons between the amplified and non-amplified

performances in which the answers given are very consistent.

This is an indication that a deeper investigation of non amplified performances should

be conducted in order to come up with relations between objective measurements and

subjective evaluations.

C8_S1

(Theatre of Ancient Epidauros)

C25_S1

(Theatre of Epidauros)

G (in dB) 5 dB -4 dB

T30 (in sec) <0,6 sec 1,2 sec

EDT (in sec) <0,3 sec 0,1 sec

Table 6.3: The values of the acoustic quantities measured in the receiver positions which are the

closest to the recording positions used for this part of the listening tests.

Conclusions and future work

76

7. Conclusions and future work

7.1. Conclusions

In the present study, it has been attempted to approach the matter of investigating the

acoustics of Ancient Greek and Roman theatres under the light of their modern use.

By combining results from objective acoustic measurements, computer simulations

and listening tests a “holistic” way of studying the issue has been proposed.

With the help of the in situ measurements it has been possible to observe that in the

present conditions of the theatres the source position does not have an influence on

the acoustic properties of the theatre which in terms of strength are mainly affected by

the distance between source and receiver.

Specifically for the Theatre of Epidauros by positioning the sound source where the

logeion used to be when the skene of the theatre was intact, no positive effect on the

acoustic characteristics was observed. On the contrary, an increase in T30 values was

observed when the source was positioned on the orchestra. However, as stated before

this could be an improvement for performing music (since T30 is already too low for

musical performances) but as far as speech is concerned any source position would be

just as good in terms of intelligibility.

Another interesting result that was evident in both measurements and simulations is

that when the theatre is not occupied, the reflections arriving to the first kerkida from

the surfaces that are in opposite side (and vice versa) could be experienced as a

distinct echo. The computer simulation showed that this effect could be smoothened

by the addition of a stage. Although after adding the stage T30 and G do not increase

much, the effect is obvious on EDT and consequently on C80. However, even if C80

decreases STI still remains at quite high values around 0,65.

In the Theatre of Ancient Epidauros the wooden panel positioned at the back of the

stage seemed to create an increase in the EDT when the receiver was approaching to

the axis of symmetry of the theatre. This fact causes C80 to drop to low values in the

middle kerkida although for the specific theatre this is not so important because its

size is quite small and the values of C80 and STI are high in most positions. This

phenomenon was not observed at the simulations. The agreement of the measured and


77

simulated values was not as good as in the Theatre of Epidauros, basically due to

difficulties in defining successfully diffusion and scattering coefficients in the

surfaces of the modeled theatre. However, from the relative results between the model

with and without the stage it was possible to observe that the addition of the stage in

the Theatre of Ancient Epidauros has similar results as in the Theatre of Epidauros. It

has to be stressed that the comparison between measured and simulated data is

focused in the case where the sound source is situated on the orchestra.

According to the results of the listening tests, the use of amplification systems in both

theatres has to be treated with extra care since the characteristics and settings of the

system, define in a great extent the sound field, and in a way they “denude” the

theatre from its natural acoustically perceived spatial properties, which they are only

underlined by the visual cues.

It is also important to be stated that the existence of a common sound amplification

system (normally comprised of 2 columns of loudspeakers positioned in the left and

right side of the stage) increases the danger of a shifted auditory image for the people

seating close to the loudspeakers. As shown in the first part of the listening tests, the

danger is higher in the Theatre of Ancient Epidauros because it is smaller and the

loudspeakers are usually positioned closer to the seating area.

However, the loudspeaker system increases greatly the level in all positions, allowing

the spectators which are seating at the most remote positions to be able to follow with

no effort the performance. This is not so important in the Theatre of Ancient

Epidauros since its size is much smaller. Finally, according to the results of the

listening tests the use of a loudspeaker system also improves the feeling of acoustical

“intimacy” for the spectators, which seems to be related to the level of the sound.

Many obstacles appeared all along the way of this project and in all the different

stages. Some of them have been discussed in this study.

For example:

• The effect of the weather conditions in the outdoor measurements (observed in

the measurements from source position S3, at the Theatre of Epidauros)


78

• The difficulty of assigning absorption and scattering characteristics to the

surfaces in the models of the theatres in order to obtain a good agreement

between measured and simulated results

• The difficulty of designing/conducting listening tests and interpreting the

results

Some other problems related to the organization of a project like this, the realization

of which depends on many individuals and authorities cannot be shown or evaluated.

However, planning has been an important part of this project and it deserves to be

mentioned. The interaction with people from different disciplines (public servants

from different related authorities - archaeologists, engineers, artists, producers,

philologists) that is needed to organize and conduct a project like this is part of the

learning process; moreover, it is necessary in order to be able to perceive the issue of

the modern use of Ancient Greek and Roman Theatres from all the different points of

view.

7.2. Future work

First of all, the models of the theatres should be further improved in order to give

results that are in better agreement with the measured data.

As far as the effect of the source position on the acoustical behavior of the theatres

under consideration, further investigation of the measured data is required.

Furthermore, comparison of the measured data, with simulations of other source-

receiver configurations, is needed. For investigating specifically the positions of the

sound sources proposed by Vitruvius [6] for the Theatre of Epidauros, the theatre

should be modeled in its initial form.

In terms of relating objective parameters with measured data, more listening tests

should be conducted; as far as “Intimacy” is concerned the relation with parameters

like LG or LEF (which are known to be related with subjective parameters as Listener

Envelopment and Apparent Source Width, respectively) could be studied.

There is a necessity for acoustical measurements in the occupied theatres. Those data

could help in retuning the models and approach the modern use of the theatres from a

more realistic point of view.

References

79

8. References

[1]: ICOMOS, “Principle for the analysis, conservation and structural restoration of

Architectural Heritage”, 2003.

[2]: “Burra Charter”, Ar.18, 1999.

[3]: The Australia ICOMOS Charter, “For the Conservation of places of Cultural

significance”, 1999.

[4]: ERATO: “Final Report: covering period from 1 February 2003 to 31 January

2006”.

[5]: Michel Vallet, Bruno Vincent, Martin Lisa Nielsen, “Report on the Assessment of

the Virtual Environments”, ERATO: Deliverable 9.4. November 2005.

[6]: Vitruvius, “The Ten Books on Architecture”, Translated by Morris Hicky

Morgan, Ph.D., LL.D., Dover Publications, Inc., New York.

[7]: Technical Note 001, “Measuring Impulse Responses using DIRAC”, Acoustics

Engineering, February 2004.

[8]: ISO 2005, “Annex A (informative), Auditorium measures derived from impulse

responses”, ISO/CD 3382-1, 2005.

[9]: L. Cremer, ”Different Distributions of the Audience”, Auditorium Acoustics,

Applied Science Publishers LTD, London 1975.

[10]: H. Kuttruff, ”Room Acoustics”, Fourth Edition, Spon, London, 2000.

[11]: Finn Jacobsen, “Lecture notes for course 31260, Advanced Acoustics, Ex9.

Outdoor Sound Propagation”, Acoustic Technology, Oersted DTU, 2006.

Appendix

80

9. Appendix

9.1. T30 versus T20

For concert halls, T20 is considered to be a more reliable descriptor of the

reverberation time in concert halls/auditoriums, since T30 is more “vulnerable” to

background noise. However, on the Figures that follow below it is possible to observe

how close the values for T20 agree with the ones for T30, when plotted versus

distance, but versus frequency as well. As expected, the values for T20 are generally

somewhat lower than the values for T30. Furthermore, with the current version of

ODEON it is easier to obtain results and graphs for T30, rather than T20. Considering

that a large part of the analysis presented in this report is based on results obtained

from ODEON simulations, and keeping in mind that the real measurements showed a

close agreement between T20 and T30, it was decided to use the parameter T30 for

evaluating reverberation time in both theatres.

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00

Distance [m]

Reverberation Tim

e [sec]

S1_T20

S1_T30

Figure 9.1: Reverberation Time versus distance at the Theatre of Epidauros. The source is


500Hz and 1000Hz octave bands, for the specific receiver position [8]. The pink and blue line,

indicate the measured values for T20 and T30, respectively.

Appendix

81

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

100 1000 10000

Frequency [Hz]

Reverberation Tim

e [sec]

S1_T20

S1_T30

Figure 9.2: Reverberation Time versus frequency at the Theatre of Epidauros. The source is



the measured values for T20 and T30, respectively.

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,00 5,00 10,00 15,00 20,00 25,00 30,00

Distance [m]

Reverberation Tim

e [sec]

S1_T20

S1_T30

Figure 9.3: Reverberation Time versus distance at the Theatre of Ancient Epidauros. The source


500Hz and 1000Hz octave bands, for the specific receiver position [8]. The pink and blue line,

indicate the measured values for T20 and T30, respectively.

Appendix

82

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

100 1000 10000

Frequency [Hz]

Reverberation tim

e [sec]

S1_T20

S1_T30

Figure 9.4: Reverberation Time versus frequency at the Theatre of Ancient Epidauros. The



the measured values for T20 and T30, respectively.

Appendix

83

9.2. The effect of the ground9

The sound pressure produced by a monopole in free field conditions at a distance r, is

given by:

r

Qejp

krtj

πωρ ω

4ˆ

)( −

= (9.1)

Where “ρ” is the density of the air (in kg/m3), “ω” is the angular frequency (in

rad/sec), “Q” is the volume velocity of the source (in m3/sec), “κ” is the wave number

(in m-1).

When the source is located above a rigid plane surface an additional term should be

added which represents the contribution of the image source symmetrical about the

surface.

+=

+= −

−−−

)(1444

ˆ )()()()(

dR

drd

RRjk

r

d

d

kRtj

r

kRtj

d

kRtj

eR

RR

R

Qej

R

QejR

R

Qejp

πωρ

πωρ

πωρ ωωω

(9.2)

Where “R” is the plain wave reflection coefficient of the image source, “Rd” is the

direct path length (in m), “Rr” is the reflected path length (in m).

If the floor of the orchestra is assumed to be a totally reflecting surface then the plain

wave reflection coefficient R can be assumed to be equal to unity and the first

equation can be simplified to:

+=+= −

−−−)(

)()()(

1444

ˆ dr

drd

RRjk

r

d

d

kRtj

r

kRtj

d

kRtj

eR

R

R

Qej

R

Qej

R

Qejp

πωρ

πωρ

πωρ ωωω

(9.3)

Taking as reference the sound pressure produced by the monopole in free field

conditions, it is possible to express the last equation in dB.

+=

−

2

)(

2

1log10ˆ

ˆlog10 dr RRjk

r

d

ref

eR

R

p

p (9.4)

Plotting the equation given above for different receiver points, it is possible to see in

which frequencies the pressure reaches its minima for each receiver position.

9 The theoretical analysis concerning the effect of a rigid plane surface in the sound field of a monopole

can be found in [11].

Appendix

84

In the case of this analysis, for low frequencies it is possible to assume that the sound

source behaves as a monopole, the floor of the orchestra is totally reflecting and the

seating area can be approximated by a tilted surface (Figure 9.5).

In the Table 9.1, the positions of the receivers for the Theatre of Epidauros can be

found. With simple geometrical calculations the direct (Rd) and the reflected (Rr) path

length can be calculated and in Figure 9.6 to Figure 9.10 the effect of the ground

reflection can be seen for the different receiver positions.

Figure 9.5: The receiver (red dot on black line) receives both the direct sound and the reflection

coming from the orchestra floor. The black dot on the solid black line and the black dot on the

dashed line indicate the real and the image source, respectively. The notations HS, HR and D

stand for “Height of Source from the ground”, “Height of Receiver from the ground” and

“Horizontal Distance between Source and Receiver”, respectively.

Row HS [m] HR [m] D [m]

5 1,50 2,50 17,50

15 1,50 6,00 23,50

25 1,50 9,60 29,50

38 1,50 16,20 41,50

48 1,50 20,00 47,50

Table 9.1: Table of values for the Theatre of Epidauros.

HR

D

HS

Appendix

85

For the receiver points at the Theatre of Epidauros the first minimum in the pressure

occurs around 400Hz for the receivers which are closer to the source, while for the

ones which are further away it occurs between 100 and 200Hz.

In the real case, where the floor of the orchestra is not totally reflecting, the minima

shown above will shift towards even lower frequencies. This phenomenon most likely

explains why in the measured data at the Theatre of Epidauros, Strength takes

relatively low values in frequencies below 500Hz.

Figure 9.6: The effect of the interference of the direct sound and the reflection coming from the

floor of the orchestra, on the sound pressure measured at the 5th row of the Theatre of Epidauros.

The floor of the orchestra is considered totally reflecting.

Appendix

86


floor of the orchestra, on the sound pressure measured at the 15th row of the Theatre of

Epidauros. The floor of the orchestra is considered totally reflecting.




Appendix

87







Appendix

88

Following the same way of thinking it is possible to reach to similar conclusions

concerning the drop in Strength for frequencies lower than 500Hz for the Theatre of

Ancient Epidauros, as well (Table 9.2 and Figure 9.11 to Figure 9.13).

Row HS [m] HR [m] D [m]

2 1,50 1,00 8,70

8 1,50 3,50 14,10

14 1,50 5,70 18,90

Table 9.2: Table of values for the Theatre of Ancient Epidauros.


floor of the orchestra, on the sound pressure measured at the 2nd row of the Theatre of Ancient


Appendix

89


floor of the orchestra, on the sound pressure measured at the 8th row of the Theatre of Ancient



floor of the orchestra, on the sound pressure measured at the 14th row of the Theatre of Ancient


Appendix

90

9.3. Theatre of Epidauros- Grid Response ODEON plots

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

3,84

3,76

3,68

3,60

3,52

3,44

3,36

3,28

3,20

3,12

3,04

2,96

2,88

2,80

2,72

2,64

2,56

2,48

2,40

2,32

2,24

2,16

2,08

EDT at 1000 Hz > 4,00

< 2,02Odeon©1985-2006

Figure 9.14: Early Decay Time (EDT) at 1000Hz at the Theatre of Epidauros (without stage).

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

3,84

3,76

3,68

3,60

3,52

3,44

3,36

3,28

3,20

3,12

3,04

2,96

2,88

2,80

2,72

2,64

2,56

2,48

2,40

2,32

2,24

2,16

2,08

EDT at 4000 Hz > 4,00

< 2,02Odeon©1985-2006

Figure 9.15: Early Decay Time (EDT) at 1000Hz at the Theatre of Epidauros (with stage).

Appendix

91

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

1,84

1,76

1,68

1,60

1,52

1,44

1,36

1,28

1,20

1,12

1,04

0,96

0,88

0,80

0,72

0,64

0,56

0,48

0,40

0,32

0,24

0,16

0,08

T30 at 1000 Hz > 2,00

< 0,02Odeon©1985-2006

Figure 9.16: Reverberation Time (T30) at 1000Hz at the Theatre of Epidauros (without stage).

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

1,84

1,76

1,68

1,60

1,52

1,44

1,36

1,28

1,20

1,12

1,04

0,96

0,88

0,80

0,72

0,64

0,56

0,48

0,40

0,32

0,24

0,16

0,08

T30 at 4000 Hz > 2,00

< 0,02Odeon©1985-2006

Figure 9.17: Reverberation Time (T30) at 1000Hz at the Theatre of Epidauros (with stage).

Appendix

92

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

2,0

0,0

-2,0

-4,0

-6,0

-8,0

-10,0

-12,0

-14,0

-16,0

-18,0

-20,0

-22,0

-24,0

-26,0

-28,0

-30,0

-32,0

-34,0

-36,0

-38,0

-40,0

-42,0

SPL at 1000 Hz > 6,0

< -43,5Odeon©1985-2006

Figure 9.18: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Epidauros (without stage).

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

2,0

0,0

-2,0

-4,0

-6,0

-8,0

-10,0

-12,0

-14,0

-16,0

-18,0

-20,0

-22,0

-24,0

-26,0

-28,0

-30,0

-32,0

-34,0

-36,0

-38,0

-40,0

-42,0

SPL at 4000 Hz > 6,0

< -43,5Odeon©1985-2006

Figure 9.19: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Epidauros (with stage).

Appendix

93

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

16,0

14,0

12,0

10,0

8,0

6,0

4,0

2,0

0,0

-2,0

-4,0

-6,0

-8,0

-10,0

-12,0

-14,0

-16,0

-18,0

-20,0

-22,0

-24,0

-26,0

-28,0

C80 at 1000 Hz > 20,0

< -29,5Odeon©1985-2006

Figure 9.20: Clarity (C80) at 1000Hz at the Theatre of Epidauros (without stage).

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

16,0

14,0

12,0

10,0

8,0

6,0

4,0

2,0

0,0

-2,0

-4,0

-6,0

-8,0

-10,0

-12,0

-14,0

-16,0

-18,0

-20,0

-22,0

-24,0

-26,0

-28,0

C80 at 4000 Hz > 20,0

< -29,5Odeon©1985-2006

Figure 9.21: Clarity (C80) at 1000Hz at the Theatre of Epidauros (with stage).

Appendix

94

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

0,96

0,94

0,92

0,90

0,88

0,86

0,84

0,82

0,80

0,78

0,76

0,74

0,72

0,70

0,68

0,66

0,64

0,62

0,60

0,58

0,56

0,54

0,52

STI > 1,00

< 0,50Odeon©1985-2006

Figure 9.22: Speech Transmission Index (STI) at 1000Hz at the Theatre of Epidauros (without

stage).

P1P1

0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 metres

0,00

10,00

20,00

30,00

40,00

50,00 metres

0,96

0,94

0,92

0,90

0,88

0,86

0,84

0,82

0,80

0,78

0,76

0,74

0,72

0,70

0,68

0,66

0,64

0,62

0,60

0,58

0,56

0,54

0,52

STI > 1,00

< 0,50Odeon©1985-2006

Figure 9.23: Speech Transmission Index (STI) at 1000Hz at the Theatre of Epidauros (with

stage).

Appendix

95

9.4. Theatre of Ancient Epidauros-Grid Response ODEON plots

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

0,76

0,74

0,72

0,70

0,68

0,66

0,64

0,62

0,60

0,58

0,56

0,54

0,52

0,50

0,48

0,46

0,44

0,42

0,40

0,38

0,36

0,34

0,32

EDT at 1000 Hz > 0,80

< 0,31Odeon©1985-2006

Figure 9.24: Early Decay Time (EDT) at 1000Hz at the Theatre of Ancient Epidauros (without

stage).

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

0,76

0,74

0,72

0,70

0,68

0,66

0,64

0,62

0,60

0,58

0,56

0,54

0,52

0,50

0,48

0,46

0,44

0,42

0,40

0,38

0,36

0,34

0,32

EDT at 1000 Hz > 0,80

< 0,31Odeon©1985-2006

Figure 9.25: Early Decay Time (EDT) at 1000Hz at the Theatre of Ancient Epidauros (with

stage).

Appendix

96

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

0,92

0,88

0,84

0,80

0,76

0,72

0,68

0,64

0,60

0,56

0,52

0,48

0,44

0,40

0,36

0,32

0,28

0,24

0,20

0,16

0,12

0,08

0,04

T30 at 1000 Hz > 1,00

< 0,01Odeon©1985-2006

Figure 9.26: Reverberation Time (T30) at 1000Hz at the Theatre of Ancient Epidauros (without

stage).

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

0,92

0,88

0,84

0,80

0,76

0,72

0,68

0,64

0,60

0,56

0,52

0,48

0,44

0,40

0,36

0,32

0,28

0,24

0,20

0,16

0,12

0,08

0,04

T30 at 1000 Hz > 1,00

< 0,01Odeon©1985-2006

Figure 9.27: Reverberation Time (T30) at 1000Hz at the Theatre of Ancient Epidauros (with

stage).

Appendix

97

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

5,0

3,0

1,0

-1,0

-3,0

-5,0

-7,0

-9,0

-11,0

-13,0

-15,0

-17,0

-19,0

-21,0

-23,0

-25,0

-27,0

-29,0

-31,0

-33,0

-35,0

-37,0

-39,0

SPL at 1000 Hz > 9,0

< -40,5Odeon©1985-2006

Figure 9.28: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Ancient Epidauros (without

stage).

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

5,0

3,0

1,0

-1,0

-3,0

-5,0

-7,0

-9,0

-11,0

-13,0

-15,0

-17,0

-19,0

-21,0

-23,0

-25,0

-27,0

-29,0

-31,0

-33,0

-35,0

-37,0

-39,0

SPL at 1000 Hz > 9,0

< -40,5Odeon©1985-2006

Figure 9.29: Sound Pressure Level (SPL) at 1000Hz at the Theatre of Ancient Epidauros (with

stage).

Appendix

98

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

12,0

10,0

8,0

6,0

4,0

2,0

0,0

-2,0

-4,0

-6,0

-8,0

-10,0

-12,0

-14,0

-16,0

-18,0

-20,0

-22,0

-24,0

-26,0

-28,0

-30,0

-32,0

C80 at 1000 Hz > 16,0

< -33,5Odeon©1985-2006

Figure 9.30: Clarity (C80) at 1000Hz at the Theatre of Ancient Epidauros (without stage).

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

12,0

10,0

8,0

6,0

4,0

2,0

0,0

-2,0

-4,0

-6,0

-8,0

-10,0

-12,0

-14,0

-16,0

-18,0

-20,0

-22,0

-24,0

-26,0

-28,0

-30,0

-32,0

C80 at 1000 Hz > 16,0

< -33,5Odeon©1985-2006

Figure 9.31: Clarity (C80) at 1000Hz at the Theatre of Ancient Epidauros (with stage).

Appendix

99

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

0,96

0,94

0,92

0,90

0,88

0,86

0,84

0,82

0,80

0,78

0,76

0,74

0,72

0,70

0,68

0,66

0,64

0,62

0,60

0,58

0,56

0,54

0,52

STI > 1,00

< 0,50Odeon©1985-2006

Figure 9.32: Speech Transmission Index (STI) at 1000Hz at the Theatre of Ancient Epidauros

(without stage).

P1P1

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 metres

0,00

5,00

10,00

15,00

20,00 metres

0,96

0,94

0,92

0,90

0,88

0,86

0,84

0,82

0,80

0,78

0,76

0,74

0,72

0,70

0,68

0,66

0,64

0,62

0,60

0,58

0,56

0,54

0,52

STI > 1,00

< 0,50Odeon©1985-2006

Figure 9.33: Speech Transmission Index (STI) at 1000Hz at the Theatre of Ancient Epidauros

(with stage).

Glossary

100

10. Glossary

Diazoma = (διάζωµα/Greek) Horizontal walkway separating the upper and lower

sections of the koilon;

Hellenic = Greek

Kerkida = (Greek; pl. kerkides) wedge-shaped seating section in the koilon;

Klimaka= (κλίµακα/Greek; pl. klimakes), Staircase between the kerkides in the koilon;

Koryphaios = (κορυφαίος/Greek) the leader of the chorus;

Koilon = (κοίλον/ Greek), theatron (hel.), cavea (lat.), seating area;

Logeion = (λογείον/Greek) stage; performances in the Hellenistic period included

actors placed on a raised platform or stage behind the orchestra and in front of the

skene; the roof of the proskenion could be employed for this purpose;

Orchestra = (ορχήστρα) the area between the Koilon and the Skene, where the chorus

performed;

Proscenion = (προσκήνιο/Greek, Proscaenium/Latin) front wall of the skene; an

acting area which projected in front of the skene; in Classical Greek theatre, the

ground-level portion immediately in front of the skene was used as an acting area; in

Hellenistic period, the proskenion was a raised platform in front of the skene; the

skene eventually included two levels, a lower level with a roof (the Hellenistic

logeion or stage) and the second story skene with openings for entrances (thyromata);

Skene = (σκηνή) the stage house;

Thymeli = (θυµέλη) the center of the orchestra of an Ancient Greek Theatre; at the

early years it was meant to be an altar and later on, a place, where the leader of the

chorus (koryphaios) was standing.

Documents

The m odern use of Ancient Greek and Roman Theatres …etd.dtu.dk/thesis/193464/oersted_dtu2877.pdf · TECHNICAL UNIVERSITY OF DENMARK Acoustic Technology Ørsted DTU By Konstantinos