Measurements with ODEON with ODEON rev.pdf · Odeon©1985-2013 Licensed to: Odeon Restricted version - research and ... 26 November 2014 Room acoustic measurements 18. 27-11-2014

27-11-2014

1

Room acoustic measurements

Jens Holger Rindel

Odeon A/S, Scion-DTU, Denmark

Background

• Room acoustic measurements have become

easier than ever

• From the most simple (hand claps)

• To the most sophisticated (new parameters for

open-plan offices)

26 November 2014 Room acoustic measurements 2

Related standards

• ISO 3382-1:2009, Acoustics - Measurement of room acoustic parameters -

Part 1: Performance spaces

• ISO 3382-2:2008, Acoustics - Measurement of room acoustic parameters -

Part 2: Reverberation time in ordinary rooms

• ISO 3382-3:2012, Acoustics - Measurement of room acoustic parameters -Part 3: Open plan offices

• ISO 9921:2003, Ergonomics – Assessment of speech communication

• ISO 14257:2001, Acoustics - Measurement and parametric description of

spatial sound distribution curves in workrooms for evaluation of their acoustical performance

• ISO 18233:2006, Acoustics - Application of new measurement methods in building and room, Acoustics

• IEC 60268-16:2011, Sound system equipment – Part 16: Objective rating of speech intelligibility by speech transmission index (Edition 4.0)


Contents

• The reverberation time – development of

methods for measurement

• Snap-shot (survey) or sine sweep (precision)

• Sources of error in measurements

• Other room acoustic parameters for auditoria

• Comparison of measurements and simulations

• Calibration of sound source

• STI measurements

• Measurements in open-plan offices

Room acoustic measurements 426 November 2014

Sabine’s set of organ pipes (1906)


Frequencies:

64 Hz – 4097 Hz(7 octaves)

W.C. Sabine, Collected papers (1922)

Decay time with 1-4 organ pipes


6 dB louder sound with 4

pipes instead of 1 –

Sound in heard longer (Δt)

T60 = 10 Δt

W.C. Sabine, Collected papers (1922)

27-11-2014

2

Measurement setup in reverberation chamber 1919


Ref.: J.W. Kopec, The Sabines at Riverbank (1997)

First standards on RT

• 1963: ISO R 354 Measurement of absorption coefficients in a reverberation room

– Loudspeaker, interrupted noise or warble tone

• 1975: ISO 3382 Measurement of reverberation time in

auditoria

– Loudspeaker, interrupted noise

– Organ pipes (all semitones in each frequency range)

– Impulses from pistol shots

– Orchestra, fortissimo passages followed by long pauses


Decay of interrupted noise


Brüel & Kjær made a level recorder with logarithmic potentiometer (1949)

Decay of impulse response (1978)

Room acoustic measurements 10

Portable setup for measuring reverberation time using a pistol shot and level

recorder (Ref. K.B. Ginn (1978). Architectural Acoustics, Brüel & Kjær, Denmark).

26 November 2014

Obs: Method not allowed after revision of ISO 3382 (1998)

Integrated impulse response


Schroeder’s integrated impulse response method (1965)

Chu: JASA 63

(1978)

Backward integration of impulse response (1982)


Reading: 0.60 s from -5 to -25 dB

Result: T20 = 1.80 s

Tape recorder – change of tape direction and speed –

B&K real time analyzer with long integration time - B&K level recorder

20 dB

0.60 s

27-11-2014

3

New method – New problems

• Influence of background noise

1. Using full record length

2. Using truncated record

3. -

4. Using full record length

with subtraction of

background noise


Chu: JASA 63 (1978)

Using a sweep signal

• Method developed by

A.C. Gade (1984)

• Each sweep covers one

octave

• Applied for 6 octave bands

(125 Hz – 4000 Hz)


Sweep and

frequency response

Impulse response

after deconvolution

ISO 18233 (2006) New methods

• MLS signals

– Periodic maximum length signal + cross correlation +

octave filter + integration =

decay curve

– Length of sequence ≥ RT

– Only for time-invariant systems – quite sensitive to

changes during the

measurement (OBS)

– Distortion causes

increased noise floor (OBS)


• Sine sweeps

– Single sweep + decon-volution + octave filter +

integration = decay curve

– Longer sweeps give

reduced noise floor

– Exponential sweep ~ pink spectrum

– Only for time-invariant systems – less sensitive

than the MLS method

– Harmonic distortion

separated from impulse

response

6 s sweep length

E, MeasuredgfedcbNoise floorgfedcbOnset timegfedcbTruncation timegfedcb

C:\...\Arb-vaerelse\Impulse response file.ImpRespFile0.wavRaw decay curve at 250Hz

time (seconds)0.70.650.60.550.50.450.40.350.30.250.20.150.10.050

SP

L(d

B)

-35

-40

-45

-50

-55

-60

-65

-70

-75

-80

-85

-90

-95

-100

-105

-110

-115

-120

Odeon©1985-2013 Licensed to: Odeon Restricted version - research and teaching only!

Noise floor


60 s sweep length



time (seconds)0.70.650.60.550.50.450.40.350.30.250.20.150.10.050

SP

L(d

B)

-35

-40

-45

-50

-55

-60

-65

-70

-75

-80

-85

-90

-95

-100

-105

-110

-115

-120

-125


Noise floor

Factor 10 –> 10 dB


300 s sweep length



time (seconds)0.70.650.60.550.50.450.40.350.30.250.20.150.10.050

SP

L(d

B)

-35

-40

-45

-50

-55

-60

-65

-70

-75

-80

-85

-90

-95

-100

-105

-110

-115

-120

-125


Noise floor

Factor 5 –> 7 dB


27-11-2014

4

Measurements

Obtain an impulse response using an impulse signal

• Sweep method

• Start pistol, hand clap, popping a balloon or a paper bag

Derive ISO 3382 parameters

Implementation in Odeon12 – our aims:

– Automatic

– Reproducible

– Give warnings when needed


• DEMO


P1

1

2

3

4

5

6

7

8

9

P1

Odeon©1985-2013 Licensed to: MULTICONSULT AS, Norway

Snap shot (handclap)

• Hole Bo – room at

elder centre

• Visit includes:

• Talking to people

about the acoustical

problems

• Taking some photos

• Recording some hand

claps


Demo


Recording of impulse response with a smart phone

Simulated Avr.gfedcbSimulated MingfedcbSimulated MaxgfedcbSimulated Std. dev.gfedcbMeasured Avr.gfedcbMeasured MingfedcMeasured MaxgfedcMeasured Std. dev.gfedc

Statistics

Active receivers: 2,5

Frequency

63 125 250 500 1000 2000 4000 8000

T(2

0)

(s)

1,5

1,4

1,3

1,2

1,1

1

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1

Odeon©1985-2013 Licensed to: MULTICONSULT AS, Norw ay

Acoustic survey made with hand claps

10 10% absorbentgfedcb 10005 Glass, large gfedcb 1002 !Brick, unglagfedcb 3002 Wood parquet gfedcb 4044 2*13 mm plastgfedcb 20 20% absorbentgfedcb 12100 (Example 1210gfedcb 3075 Panel, 13 mm gfedcb 4058 Adjusted mategfedcb 11057 Chairs, lightgfedcb 3004 Wooden f loor gfedcb

Absorption coeff icients

Frequency (Hz)

63 125 250 500 1000 2000 4000 8000

1

0,95

0,9

0,85

0,8

0,75

0,7

0,65

0,6

0,55

0,5

0,45

0,4

0,35

0,3

0,25

0,2

0,15

0,1

0,05

Odeon©1985-2013 Licensed to: MULTICONSULT AS, Norw ay26 November 2014 Room acoustic measurements 23

Model with initial materials

Simulated Avr.gfedcbSimulated MingfedcbSimulated MaxgfedcbSimulated Std. dev.gfedcbMeasured Avr.gfedcbMeasured MingfedcMeasured MaxgfedcMeasured Std. dev.gfedc

Statistics

Active receivers: 2,5

Frequency

63 125 250 500 1000 2000 4000 8000

T(2

0)

(s)

1,5

1,4

1,3

1,2

1,1

1

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1


10 10% absorbentgfedcb 10005 Glass, large gfedcb 1002 !Brick, unglagfedcb 3002 Wood parquet gfedcb 4044 2*13 mm plastgfedcb 20 20% absorbentgfedcb 12100 (Example 1210gfedcb 11057 !Chairs , lighgfedcb 3004 Wooden floor gfedcb 13100 (Example 1310gfedcb 4058 Adjusted mategfedcb

Absorption coefficients

Frequency (Hz)

63 125 250 500 1000 2000 4000 8000

1

0,95

0,9

0,85

0,8

0,75

0,7

0,65

0,6

0,55

0,5

0,45

0,4

0,35

0,3

0,25

0,2

0,15

0,1

0,05



Model with adjusted materials

Acoustic survey made with hand claps

27-11-2014

5

Coming soon

• ODEON ver. 13:

• Generic algorithm to optimize absorption

coefficients of unknown materials to match a set

of measurements


Error sources in RT measurements

• Wrong onset time

• Influence of noise floor

• Distortion from loudspeaker

• Faulty impulse response (disturbance)

• Temperature and humidity


Measuring correct resultsOnset of impulse response?


Omni microphonegfedcbOnset timegfedcbTruncation timegfedcb

F:\Users\Claus\Documents\Odeon f iler\Measurements\ExtraPreImpulseA.w av

Ray Impulse response at 1000Hz

time (seconds)

21,510,50

p

10

8

6

4

2

0

-2

-4

-6

-8

-10

Odeon©1985-2013 Licensed to: OdeonElectromagnetic transfer

Time delay = r / c

r

26 November 2014

Measuring correct resultsOnset of impulse response?


E, MeasuredgfedcbE, IntegratedgfedcbE, Correctedgfedcb

F:\Users\Claus\Documents\Odeon filer\Measurements\ExtraPreImpulseA.wavDecay curves at 1000Hz T(30) = 1,91 seconds

time(seconds)21,81,61,41,210,80,60,40,20

SPL(d

B)

45

40

35

30

25

20

15

10

5

0

-5

-10

Odeon©1985-2013 Licensed to: Odeon

Wrong onset time

T(30) = 1.91 s


F:\Users\Claus\Documents\Odeon filer\Measurements\ExtraPreImpulseA.wavDecay curves at 1000Hz T(30) = 1,91 seconds

time(seconds)1,81,61,41,210,80,60,40,20

SPL(d

B)

45

40

35

30

25

20

15

10

5

0

-5

-10


Correct onset time

T(30) = 1.91 s

EDT = 2.23 s

C(80) = -26.6 dB

EDT = 1.98 s

C(80) = -0.6 dB

26 November 2014

Measuring correct resultsTruncation time of impulse response


D:\Measured Impulse responses\isra_measurements1\Auditorium21GEorgeClaus15feb2013\s1r1_4000.wavRaw decay curve at 4000Hz

time (seconds)3.83.63.43.232.82.62.42.221.81.61.41.210.80.60.40.20-0.2

SPL(d

B)

-8

-10

-12

-14

-16

-18

-20

-22

-24

-26

-28

-30

-32

-34

-36

-38

-40

-42

-44

-46

-48

-50

-52

-54

-56

-58

-60

-62

-64

-66

Odeon©1985-2013 Licensed to: Odeon A/S

Noise floorTt

Truncation time

26 November 2014


F:\Users\C laus\Documents\Odeon filer\Measurements\Auditorium 21\RevisedOdeon12\ISRA_measurementsAuditorium21_8March\Low Gain\S1R5_sweep8000.wavDecay curves at 1000Hz T(30) = 10,61 seconds

time(seconds)3,83,63,43,232,82,62,42,221,81,61,41,210,80,60,40,20

SPL(d

B)

-35

-40

-45

-50

-55

-60

-65

-70

-75

-80

-85

-90

-95

-100

-105



F:\Users\Claus\Documents\Odeon filer\Measurements\Auditorium 21\RevisedOdeon12\ISRA_measurementsAuditorium21_8March\Low Gain\S1R5_sweep8000.wavDecay curves at 1000Hz T(30) = 1,90 seconds

time(seconds)1,41,31,21,110,90,80,70,60,50,40,30,20,10

SPL(d

B)

-32

-34

-36

-38

-40

-42

-44

-46

-48

-50

-52

-54

-56

-58

-60

-62

-64

-66

-68

-70

-72

-74

-76

-78

-80

-82

-84

-86

-88

-90


Measuring correct resultsInfluence of noise floor


T(30) = 10.6 s T(30) = 1.9 s

Evaluation range for T(30): -5 dB to -35 dB

26 November 2014

27-11-2014

6


F:\Users\Claus\Documents\Odeon filer\Measurements\Auditorium 21\RevisedOdeon12\ISRA_measurementsAuditorium21_8March\S1R1_sweep4000.wavRaw decay curve at 1000Hz

time (seconds)3210

SPL(d

B)

-30

-35

-40

-45

-50

-55

-60

-65

-70

-75

-80

-85

-90

-95

-100

-105

-110


Measuring correct resultsCompensate for truncation & background noise


1) Truncate at noise floor

2) Option: add truncated decay

Subtract noise floor

26 November 2014

Measuring correct results


Measured with exponential sine sweep according to ISO 18233

Longer sweep means

lower noise floor

Derived T30 at 1000 Hz with different S/N ratios

without and with corrections

Non-linear decays

• Non-linearity parameter

– Warning if ξ > 10 ‰ Look at the decay curve!

• Degree of curvature

– Warning if C > 10 % Look at the decay curve!


ISO 3382-2: 2008 Annex B

[‰] )1(10002

r−=ξ

( ) [%] 110020

30 −⋅=T

TC

Measuring correct resultsWarning for suspisious impulse response


3382-2 Reverberation time in ordinary rooms - the degree of non-linearity:

• r is the correlation coefficient for linear regression line

• ξ > 10‰ : warning that decay may be suspicious – visual inspection recommended

)1(10002

r−⋅=ξ

26 November 2014

35

Temperature and humidity

• NS/ISO 3382-1:2009

- 9.2 Test report

• NS/ISO 3382-2:2008

- 9.2 Test report

36

27-11-2014

7

37

Example – Project for a new church

P12

34

56

78

910

1112

1314

1516

P1


0 10 20 30 40 metres

0

10

20

30 metres

P1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

P1


38

Influence of humidity

Air absorption

10000 Solid gl

10005 Glass, l

1002 Brick, u

11057 Chairs,

80 80% abso

102 Smooth c

4048 30 mm pl

Absorption area distributed on materials

Frequency (Hz)

63 125 250 500 1000 2000 4000 8000

m² Sabin

e

655.36

573.44

491.52

409.6

327.68

245.76

163.84

81.92


Air absorption

10000 Solid gl

10005 Glass, l

1002 Brick, u

11057 Chairs,

80 80% abso

102 Smooth c

4048 30 mm pl

Absorption area distributed on materials

Frequency (Hz)

63 125 250 500 1000 2000 4000 8000

m²

Sa

bin

e

1,310.72

1,146.88

983.04

819.2

655.36

491.52

327.68

163.84


20°C 90% RH

“Summer”

20°C 20% RH

“Winter”

39

Lower limits of RT

4026 November 2014 Room acoustic measurements Rindel (ca. 1984)

Measurement uncertainty


Calculated according to ISO 3382-2: 2008 Annex A

Survey Engineering Precision

LS positions 1 2 3

Mic positions 2 3 4

Positions 2 6 12

Room acoustic parameters


ISO 3382-1 Parameter SymbolJust noticeabledifference (JND)

Early Decay Time EDT [s] 5%

Reverberation Time (20 dB range) T20 [s] 5%

Reverberation Time (30 dB range) T30 [s] 5%

Clarity (80 ms) C80 [dB] 1 dB

Definition (50 ms) D50 0.05

Centre Time Ts [ms] 10 ms

Sound Strength G [dB] 1 dB

SupportSTEarly [dB]

STLate [dB]-

26 November 2014

27-11-2014

8

Case study - Auditorium


P1

1

2

3

4

5

6789

101112131415

P1


Auditorium 21, Technical University of Denmark

Volume 1175 m3

T30@1000 Hz = 1.90 s

26 November 2014

Case study - Auditorium

Room acoustic measurements44

EDT at 1000 Hz

Distance

R3 a

t 4

,55 m

R2 a

t 6

,84 m

R5 a

t 8

,95 m

R1

at

10

,12 m

R4

at

12

,76 m

ED

T (

s)

2,4

2,2

2

1,8

1,6


T(30) at 1000 Hz

Distance

R3

at

4,5

5 m

R2

at

6,8

4 m

R5

at

8,9

5 m

R1 a

t 1

0,1

2 m

R4 a

t 1

2,7

6 m

T(3

0)

(s)

2,1

2

1,9

1,8

1,7

Odeon©1985-2013 Licensed to: OdeonSPL at 1000 Hz

Distance

R3 a

t 4

,55 m

R2 a

t 6

,84 m

R5 a

t 8

,95 m

R1

at

10

,12 m

R4

at

12

,76 m

SP

L (

dB

)

20

18

16

14

12


C(80) at 1000 Hz

Distance

R3 a

t 4,5

5 m

R2 a

t 6,8

4 m

R5 a

t 8,9

5 m

R1

at 1

0,1

2 m

R4

at 1

2,7

6 m

C(8

0)

(dB

)

2

1

0

-1

-2

-3


Measurement

Simulation

5 receiver positions

26 November 2014

Reproducibility – position7 repetitions with small changes to position


5

10

11

12

13

14

15


-0.1 m

0.1 m

0.3 m

-0.3 m

-0.2 m

0.2 m

P1

1

2

3

4

5

6789

101112131415

P1


26 November 2014

Reproducibility – positionEDT


Simulated Avr.gfedcbSimulated MingfedcbSimulated MaxgfedcbSimulated Std. dev.gfedcbMeasured Avr.gfedcbMeasured MingfedcbMeasured MaxgfedcbMeasured Std. dev.gfedcb

Statistics

Active receivers: 5,10,11,12,13,14,15

Frequency

125 250 500 1000 2000 4000

ED

T (

s)

2

1,8

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

0


26 November 2014

Reproducibility – positionSPL (strength, G)



Statistics


Frequency

125 250 500 1000 2000 4000

SP

L (

dB

)

18

17

16

15

14

13

12

11

10

9

8


26 November 2014

Reproducibility – positionC80



Statistics


Frequency

125 250 500 1000 2000 4000

C(8

0)

(dB

)

10

9

8

7

6

5

4

3

2

1

0

-1


26 November 2014

27-11-2014

9

PAUSE


Geilo Kulturkyrkje

Acoustical measurements 2013-09-

27

Jens Holger Rindel

0 5 10 15 20 25 30 metres

0

5

10

15

20 metres

P1

P2

1

2

3

4

5

6

7

8

9


0 5 10 15 20 25 30 metres

0

5

10

15

20 metres

P1P2123456

7

89


27-11-2014

10


Reverberation time, T30

Simulated Avr.gfedcbSimulated MingfedcbSimulated MaxgfedcbSimulated Std. dev.gfedcMeasured Avr.gfedcbMeasured MingfedcbMeasured MaxgfedcbMeasured Std. dev.gfedcb

Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

T(3

0)

(s)

1,8

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

0


Simulated Avr.gfedcbSimulated MingfedcbSimulated MaxgfedcbSimulated Std. dev.gfedcMeasured Avr.gfedcbMeasured MingfedcbMeasured MaxgfedcbMeasured Std. dev.gfedcb

Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

T(3

0)

(s)

1,8

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

0


27-11-2014

11

EDT

Simulated Avr.gfedcbSimulated MingfedcSimulated MaxgfedcSimulated Std. dev.gfedcMeasured Avr.gfedcbMeasured MingfedcbMeasured MaxgfedcbMeasured Std. dev.gfedcb

Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

ED

T (

s)

2,4

2,2

2

1,8

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

0



Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

ED

T (

s)

2

1,8

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

0


Clarity, C80


Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

C(8

0)

(dB

)

11

10

9

8

7

6

5

4

3

2

1

0



Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

C(8

0)

(dB

)

10

9

8

7

6

5

4

3

2

1

0

-1


Sound strength, G


Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

SP

L (

dB

)

24

22

20

18

16

14

12

10

8

6

4

2



Statistics


Frequency

63 125 250 500 1000 2000 4000 8000

SP

L (

dB

)

24

22

20

18

16

14

12

10

8

6

4

2

0

-2


Support, STearly and STlate

Simulated

Measured

Receiver: 8

Frequency (Hertz)

63

125

250

500

10

00

20

00

40

00

80

00

ST

(Earl

y)

(dB

)

7,68

5,12

2,56

0

-2,56

-5,12

-7,68

-10,24

-12,8

-15,36

Simulated

Measured

Receiver: 8

Frequency (Hertz)

63

125

250

500

10

00

20

00

40

00

80

00

ST

(La

te)

(dB

)

7,68

5,12

2,56

0

-2,56

-5,12

-7,68

-10,24

-12,8

-15,36

-17,92

-20,48

-23,04

Diffuse field calibration

27-11-2014

12

Speech Transmission Index

• Originally based on the MTF (Modulation Transfer Function)

• Houtgast & Steeneken (1973)

– 14 modulation frequencies

– 7 octave bands

– Very time consuming measurement

• Schroeder showed that the MTF is the Fourier transform of the squared impulse response

• Schroeder (1981)

– Very quick measurement

– Background noise can be included in the calculation of STI

(afterwards)


STI measurements

• Talker and listener in same room

– Source directivity and calibration should follow the

relevant standard

• Room with sound reinforcement system or PA or

VA system

– The measuring signal can be injected directly to the sound system

– The sound level is controlled by the sound system


Open plan offices – ISO 3382-3

• RT is not sufficient

– (but may be measured according to Part 2 of ISO

3382)

• New parameters include

– Spatial decay rate of speech

– Distraction distance (STI = 0.5)

– Privacy distance (STI = 0.2)

– Background noise level


STI and speech intelligibility


ISO 9921:2003, Fig. F.1

STI: Speech transmission Index

SRT: Speech Reception Threshold

PB: Phonetically Balanced

CVC: Consonant – Vocal – Consonant

EQB: Equally Balanced Phoneme Distribution

Privacy – Distraction distance

Open-plan office example


Measurements in open-plan offices


Simple room model is

sufficient

Only with source and receivers

Just to define distances

O

XY

Z

P11

23

45

67

P1


27-11-2014

13

Detailed model made with SketchUp

26 November 2014 73Room acoustic measurements 26 November 2014 74Room acoustic measurements

Measured STI – spatial decay


Measured STI

STI regression-line

Measured STI versus distance - distraction distance /privacy distance

rD = 11,92 metres,rP = 23,91 metres

Distance (metres)

R1

at

1,7

0 m

R2

at

6,9

0 m

R3

at

9,4

5 m

R4 a

t 1

1,2

0 m

R5 a

t 1

3,4

5 m

R6 a

t 1

7,7

0 m

R7 a

t 1

9,4

5 m

STI

0,8

0,7

0,6

0,5

0,4

0,3


Measured spatial decay of A-weighted speech


Measured SPL

D2,S curve

Free field (6dB dd)

Measured spatial decay, D2,S = 10,48 dB

Lp,A,S, 4 m = 55,02 dB,

10Log(distance)

R1 a

t 1,7

0 m

R2 a

t 6,9

0 m

R3 a

t 9,4

5 m

R4

at 11,2

0 m

R5

at 13,4

5 m

R6

at 17,7

0 m

Lp (

dB

)

66,56

61,44

56,32

51,2

46,08

40,96

35,84

30,72


Measurement line 1

STI all receivers

0,8

5

0,6

0

0,5

0

0,46

0,3

9

0,4

1

0,4

0

MålestørrelseAnbefalt

krav

Målt verdi

DL2,S (dB) ≥ 7 10,5

Lp,AS,4m (dB) ≤ 52 55

rD (m) ≤ 11 12

STI 0,2Figur under

STI 0,6 0,9

Measured

26 November 2014 77Room acoustic measurements

Conclusion

• Measurement of room acoustic parameters has

become easy and fast

• Using the sine sweep technique offers high

quality measurements

• However, be aware of possible erroneous

measurements

• Inspection of the measured decay curve is highly

advisable
