Acoustics RPG Diffusion

MODERN SCHOOL ACOUSTICSMODERN SCHOOL ACOUSTICS

RPG DIFFUSOR SYSTEMSRPG DIFFUSOR SYSTEMS

“RPG Diffusor Systems, Inc. ” is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Presented by:Dr. Peter D’Antonio- FASA, FAES

President/CEO, RPG Diffusor Systems

®® AIA/CES Provider J425Program AF1011

Learning ObjectivesLearning Objectives

Part 1 Introduction: Building better schools

Part 2 Acoustic t ools to design effective schools

Part 3 Suggested designs for core and ancillary learning spaces

Part 1: Building Better Schools

• There is a renewed interest in effective and sustainable school design

• AIA is focusing attention on the subject

• USGBC is focusing attention on the subject, because sustainable school design has produced unacceptable acoustical results

• PISA has carried out an international comparative trial of student performance in reading comprehension, calculus, and natural science

What is the Problem?• Existing acoustical designs have not evolved to incorporate

the current state-of-the-art and the result is schools are failing to meet their intended goals

• Existing acoustical designs are limited to conventional acoustical materials, like thin fabric wrapped panels, ACT and simple curved reflectors, which cannot address all of speech intelligibility and music appreciation challenges

• Even with adequate budgets, there is a false sense of economy in short term goals, rather than factoring costs over the life of the project and the long term effects on the students and teachers

• Selfish goals of special interest groups, like HVAC industry, to resist lower background noise standards

• Failure to recognize that we have a problem and repeat past mistakes

• Budgeting Agencies – It may take an increase in school budgets to insure

success

What is the solution?• Recognize that we have a problem• Stop using current school designs for core learning spaces,

like classrooms and lecture halls • Stop using current school designs for ancillary learning

spaces like band rooms, practice rooms and auditoria• Begin adopting ANSI 12.6 to control reverberation,

background noise and noise intrusion– It’s not the answer, but it is a beginning

• Consider the ideas presented today, which may seem heretical and revolutionary until adopted

• Proceed one step at a time and adopt the ideas presented today in limited areas– Convert one lecture hall and let the school hear the

difference– Convert one band room, watch the students select it

over others• Begin collaborating with progressive acousticians

Importance of Acoustics in Education

6. Acoustics

10. Acoustics

ArchitectureDec-2003

pg 122

USGBC Member

• RPG supports the mission of the USGBC to promote buildings that are environmentally responsible, profitable and healthy places to live and work.

• In 1995, the USGBC developed the LEED Rating System for developing high-performance, sustainable buildings.

• Members of the USGBC representing all segments of the building industry developed LEED and continue to contribute to its evolution.

• RPG offers the services of a LEED AP • Many products may be used to apply for LEED Credits

• USGBC is primarily concerned with energy and sustainability issues. However, they became interested in acoustics, because many of the studies in sustainable designs showed dissatisfaction with the acoustics.

ANSI S12.60-2002

• Adopted by USGBC- Enhanced Acoustical Performance

Provide classrooms that facilitate better teacherProvide classrooms that facilitate better teacher--student and studentstudent and student--student communicationstudent communication

Possible LEED Credits• Credit Opportunities for Wood Products

– MR Credit 3.1/3.2 Material Reuse (1-2 pts)– MR Credit 4.1/4.2 Recycled Content (1-2 pts)– MR Credit 5.1/5.2 Regional Materials (1-2 pts)– MR 6 Credit Rapidly Renewable Materials (1 pt)– MR Credit 7: Certified Wood- FSC Cores/Veneers (1 pt)– EQ Credit 4.1: Low-Emitting Adhesives & Sealants (1 pt)– EQ Credit 4.2: Low-Emitting Paints and Coatings (1 pt)– EQ Credit 4.4: Low-Emitting Substrates (Cores) (1 pt)

• Credit Opportunities for Glass Reinforced Gypsum Products– MR Credit 4.1 and 4.2: Recycled content (10-40%)– EQ Credit 4.1 and 4.2: Low Emitting Adhesives/Paints

• Credit Opportunities for Upholstered Products– MR Credit 4.1 and 4.2: Recycled content

• Credit Opportunities for Microperforated Plastic Absorbers– EA Credit 1: Daylighting (1-10 pts)

• Credit Opportunities for Isolation Materials– MR Credit 4.1/4.2 Recycled Content (1-2 pts)

• Credit Opportunity for Enhance LEED for Schools (1pt)– STC Core Learning and Ancillary Learning Spaces

LEED for Schools V3

60Not Addressed60Core learning to music room, mechanical room,

cafeteria, gymnasium, indoor swimming pool

45 ‐ 50Not Addressed45 ‐ 50Core learning to corridor, staircase, office or

conference room

53Not Addressed53Core learning to common use and toilet rooms

50Not Addressed50Core learning to core learning

Sound Transmission Class (STC) Core Learning *

* Includes building services AND exterior noise in determining total permissable background noise levels

35 ‐ 40 (HVAC only)45 (HVAC only)40 *> 20,000 ft3 (and all ancillary spaces)

35 ‐ 40 (HVAC only)45 (HVAC only)35 *> 10,000 ft3 < 20,000 ft3

35 ‐ 40 (HVAC only)45 (HVAC only)35 *< 10,000 ft3

Background Noise (dBA)

OR total area of wall panels, ceiling finishes and other sound absorbant finishes equals or exceeds total ceiling area.

* 100% of all ceiling areas (excluding lights, diffusers and grills) in all classrooms and core learning spaces are finished with min. 0.7 materials

< 1.5< 1.5< 1.5> 20,000 ft3 (and all ancillary spaces)

NRC 0.7 *NRC 0.7 *0.7> 10,000 ft3 < 20,000 ft3

NRC 0.7 *NRC 0.7 *0.6< 10,000 ft3

Reverberation Time for Core Learning Spaces

LEED EnhancedLEED MinimumANSI 12.6 (1)

Note that these are minimum ratings and good design practice increases the STC of the door window assemblies to approach the wall STC rating

* Windows are allowed an STC‐35 rating and core learning doors an STC‐30 rating. Doors for entry into music rooms are allowed an STC‐40 rating

LEED for Schools V3

Note that these are minimum ratings and good design practice increases the STC of the door window assemblies to approach the wall STC rating

* Windows are allowed an STC‐35 rating and core learning doors an STC‐30 rating. Doors for entry into music rooms are allowed an STC‐40 rating

60Not Addressed60Office or conference room to mechanical room, cafeteria, gymnasium, indoor swimming pool

45Not Addressed45Office or conference room to outside

45Not Addressed45Office or conference room to office or conference room

60Not Addressed60Office or conference room to music room

45Not Addressed45Office or conference room to corridor, staircase, common use and toilet rooms

60Not Addressed60Music room to mechanical room, cafeteria, gymnasium, indoor swimming pool

45Not Addressed45Music room to outside

60Not Addressed60Music room to office or conference room

60Not Addressed60Music room to music room

60Not Addressed60Music room to corridor, staircase, common use and toilet rooms

45 ‐ 55Not Addressed45 ‐ 55Corridor to mechanical room, cafeteria, gymnasium, indoor swimming pool

45Not Addressed45Corridor to outside

45Not Addressed45Corridor to office or conference room

60Not Addressed60Corridor to music room

45Not Addressed45Corridor to corridor, staircase, common use andtoilet rooms

Sound Transmission Class (STC) Ancillary Learning Space *

LEED for Schools V3

* Applies to renovations only. New construction the spaces shall not be located above core learning spaces

Not AddressedNot Addressed60*Gymnasia, dance studios or other high impact

activity rooms above ancillary learning rooms

Not AddressedNot Addressed65*

Gymnasia, dance studios or other high impact activity rooms above core learning rooms> 20,000 ft3

Not AddressedNot Addressed70*

Gymnasia, dance studios or other high impact activity rooms above core learning rooms< 20,000 ft3

Not AddressedNot Addressed45Floor/ceilings above ancillary learning spaces

Not AddressedNot Addressed45 ‐ 50Floor/ceilings above core learning areas

Impact Isolation Class (IIC)

(1) ANSI 12.6 Does not apply to: Special purpose classrooms, Tel(1) ANSI 12.6 Does not apply to: Special purpose classrooms, Teleconferencing econferencing rooms, Special Ed rooms and Large Auditoriarooms, Special Ed rooms and Large Auditoria

PISA:Programme for International Student Assessment

OECD:Organisation for Economic Co-operation and

Development

International comparative trial of student performancein reading comprehension,

calculus, and natural science

e

o

e

Leistungen und Lesen im Internationalen BereichStudent performance in reading comprehension,

international comparison

Part 2: AcousticToolsREFLECTION

ABSORPTION DIFFUSION

• Gymnasium

• Natatorium

• Restaurant

• Library

• Atrium

• Lobby Category 2:Sound

ReproductionCategory 3:

NoiseControl

Category 1:Sound

Production

• Concert Hall

• Recital Hall

• Auditorium

• Theatre

• Studio• Recording

BroadcastStudios

• Distance Learning

• Home Theater

Category 4:Speech

Core Learning SpacesCore Learning Spaces

The Whole Picture

802

080

2

80

, 10 log

ms

ms

p dt

C dB

p dt∞=∫

∫

Quantified Ratio of Sound Field’s Energy -

Objective Measures

Integrated sound energy arriving before 80 ms to that arriving after 80 ms, C80, was > 3.

Human Perception - Subjective Measures

The music was very clear and articulate. I could understand the speaker and felt very close to her.

Architectural Design - Volume, Shape, Surface Treatment, HVAC…..

The ceiling should be 20’ above the stage and constructed of GWB & Omniffusors. The rear wall should constructed from 8” . . .

Noise Control

Flanking sound

Good noise and vibration Good noise and vibration design requires control of design requires control of transmission and flanking transmission and flanking paths. paths.

Springs and elastomers are Springs and elastomers are used to isolators floors used to isolators floors ceilings and walls. ceilings and walls.

Sound ControlSound is Sound is attenuated by attenuated by absorptionabsorption

Redirected Redirected by reflectionby reflection

Uniformly Uniformly scattered by scattered by diffusiondiffusion

Good architectural acoustic sound control design requires an appropriate combination of absorptive,absorptive, reflective reflective and diffusivediffusive surfaces

Comprehensive Reference Texts

Architectural Acoustics by M. Mehta, J. Johnson & J. Rocafort deals with sound control and acoustical design in large spaces including auditoriums, arenas, theaters, lobby areas, swimming pools, and multipurpose rooms. Typical problems include excessive reverberation (echo), which causes poor speech intelligibility, and excessive noise during events.

Acoustic Absorbers and Diffusers: Theory, Design and Application by T.J. Cox and P. D’Antonio (Taylor & Francis 2009) is a comprehensive treatment of what is currently known about the theory, design and application of acoustical surface treatments.

Master Handbook of Acoustics by F. Alton Everest, with chapters by P. D’Antonio and other contributors. This is an excellent introduction to acoustics. The author explains acoustical concepts without the use of mathematical formulas and provides useful practical information.

Part 2 - Acoustic Tools: Absorption

Process by which sound is attenuated due to frictional losses as it passes through the pores in the absorber. Sound energy is converted into heat.

Incident SoundIncident Sound(100%)(100%)

WALLWALL

Reflected SoundReflected Sound(19%)(19%)

Absorbed Sound (81%)Absorbed Sound (81%) Finish MaterialFinish Material

Types of Absorbers

Resonator AbsorberThe Helmholtz resonator is a vibrating mass of air in the neck against the volume of air in the larger volume acting as a spring.

Porous AbsorberContains interconnected voids and sound is absorbed by conversion to heat due to friction.

Membrane AbsorberThe membrane absorber is a limp mass that vibrates at a specific frequency and moves air through a porous panel converting sound into heat.

d

ta

R

PP

D

d

∅=2a

t

Rev Room Method to Measure aa

Material Sample [ii]Material Sample [ii]

DiffusorsDiffusors

LoudspeakersLoudspeakersMicrophonesMicrophones

No Sample [i]No Sample [i]

50 100 150 ms

V

0

4

-4

-8

[i]

[ii]

Room impulse response Integrated impulse response

50 100 150 ms

dB

-10

-20

-30

-40

[i]

[ii]

ba

T60 = 0.05 V/ST60 = 0.05 V/Saa

V= volumeV= volume

S= surface areaS= surface area

a = absorptiona = absorption

coefficientcoefficient

Quantifying Absorption

NRC NRC -- Noise Reduction CoefficientNoise Reduction Coefficient•• Average of absorption coefficients 250 Hz through 2 kHzAverage of absorption coefficients 250 Hz through 2 kHz

•• Ranges between 0.0 (0%) & 1.0 (100%)Ranges between 0.0 (0%) & 1.0 (100%)

•• ExamplesExamples: 5/8: 5/8”” ACT ACT vsvs Low Frequency ResonatorLow Frequency Resonator

FrequencyFrequency 125 Hz125 Hz 250 Hz250 Hz 500 Hz500 Hz 1 kHz1 kHz 2kHz2kHz 4kHz NRC4kHz NRC

ACTACT 0.080.08 0.250.25 0.600.60 0.800.80 0.820.82 0.81 0.650.81 0.65

ResonatorResonator 0.900.90 0.800.80 0.500.50 0.250.25 0.150.15 0.150.15 0.430.43

NRC is not a valid indicator of the effectiveness NRC is not a valid indicator of the effectiveness of the absorber, if you need low frequency of the absorber, if you need low frequency

absorption!absorption!

Frequency Dependent Absorbers

• High Frequency Absorbers– Fabric wrapped panels – ACT

• Mid Frequency Absorbers– Perforated Woods– Microperforated light transmitting plastics (new

technology)– Microperforated wood panels (new technology)

• Low Frequency Absorbers– Acoustical CMU– Metal plate resonators (new technology)

Effective Frequency of Absorbers

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300 350 400 450 500

Frequency, Hz/10

Abs

orpt

ion

Coe

ffici

ent

NRC

RR

AA DD

When Your Project Calls for a Fabric Finish

Fabric Wrapped Panels

Textile Facing

RR

AA DD

When Your Project Calls for a Wood Finish

Types of Absorptive Wood

RR

AA DD

Perforation PatternsPerforation Patterns

PerformancePerformance

Absorption is determined by three variables:

Hole diameter/spacing (% open area)

Panel thickness

Cavity depth and contents

When Your Project Calls for Fiber-Free, Visibility/Light Transmission

RR

AA DD

Absorption Mechanism

When surface perforations are the same size as a boundary layer of air.

Microperforated Panel

0.5 mm diameter holes

Glass

Air

Cav

ityIncident Sound

Reflected Sound

Viscous Losses

NEWNEW

Sound Absorption Data

1 Layer of Foil1 Layer of Foil

2 Layers of Foil2 Layers of Foil

30 mm off Glass30 mm off Glass



30 mm off Glass30 mm off Glass50 mm between layers50 mm between layers

30 mm off Glass30 mm off Glass100 mm between layers100 mm between layers

Foil & Mounting

Laser Cut MicroLaser Cut Micro--Slotted PanelsSlotted Panels

Light Transmitting Microslit

RR

AA DD

When Your Project Calls for a CMU Finish

Acoustical CMU

Acoustical Properties

Absorption Coefficient

Unslotted/SealedSlotted/SealedSlotted/Unsealed Unslotted/Unsealed

Transmission Loss

Part 2 - Acoustic Tools: DiffusionProcess by which sound energy is redirected and scattered evenly over a larger area due to the surface irregularities of the reflecting surface.

Occurs when surface irregularities are large compared to the wavelength.

Incident SoundIncident Sound

WALLWALL

Diffused SoundDiffused Sound

Finish MaterialFinish Material



Why do you need Diffusion?

Air DiffusersUniformly distribute air in a room, minimizing cold/hot zones and drafts.

Light DiffusersUniformly distribute light in a room, removing optical glare and minimizing bright and dim variations.

Sound DiffusorsUniformly distribute sound in a room, providing ambiance, even coverage and removal of acoustical glare caused by strong specular reflections

Where is Diffusion Needed?

Multi-Use Auditorium

Music Practice Rooms

Anywhere you need to:Anywhere you need to:Understand speechUnderstand speech

~ or ~~ or ~Appreciate music!Appreciate music!

Lecture RoomsBand/Orchestra Rooms

Choral Rooms

Types of Acoustic DiffusersReflection Phase GratingsReflection Phase Gratings

Binary Amplitude GratingsBinary Amplitude Gratings

Optimized WaveformsOptimized Waveforms

Design Theory of Diffusors

CAD/CAM

00001000011……..

1 0 1 1 1

Reflection Phase Grating diffusors were first introduced in the early 1980s. They consisted of divided wells, whose depths were based on quadratic residue number theory

Binary Amplitude Diffsorberswere created to provide diffusion through a variable impedance surface consisting of holes distributed according to an optimal binary sequence

Today, state-of-the-art Waveform diffusors are designed using:

Shape Optimization, which couples boundary element multi-dimensional optimization techniquesAperiodic Modulation, using optimal binary codes

Diffusion Frequency Bandwidth

Incident SoundIncident Sound

WALLWALL


Finish MaterialFinish Material



Small DepthHigh Pitches

Mid DepthMid Pitches

Small/Mid DepthHigh/Mid Pitch

Mid/Large DepthLow/Mid Pitch

Diffusion Measurement Standards• For the past 10+ years, I have been meeting with an international group of

leading acousticians to draft standards to measure scattering surfaces.

• I am proud to announce the publication of two measurement standards:• Diffusion Coefficient (d)- is a measure of the uniformity of the reflected

sound. Publication AES-4id-2001 JAES, Vol. 49 (3), pp. 148-165 (March 2001). Soon to be incorporated in ISO 17497-2– Quality: The purpose of this coefficient is to enable the design of

diffusers and to allow acousticians to compare the performance of surfaces for room design and performance specifications

• Scattering Coefficient (s)- is a ratio of the sound energy scattered in a non-specular manner to the total reflected sound energy. Publication ISO 17497-1– Quantity: The purpose of this coefficient is to characterize surface

scattering for use in geometrical room modeling programs and determine the effect of diffusion on the range of objective parameters that correlate with subjective impressions. i.e. T30, Clarity, Envelopment, etc. USELESS AS A PRODUCT SUBMITTALUSELESS AS A PRODUCT SUBMITTAL

Scattering Coefficient (ISO 17497-1)

Photo Courtesy of Jens Holger Rindel, Technical University of Denmark

Diffusion Coefficient (ISO 17497-2)

3D Goniometer

Foam wedges Foam wedges prevent reflectionsprevent reflections

SemiSemi--circular track circular track with loudspeakerwith loudspeaker

Pivot arm with sample Pivot arm with sample & microphone& microphone

Specular Specular ReflectionReflection

RedirectionRedirection

Diffuse Diffuse ReflectionReflection

Presentation Format 600

Complete Diffusor Specification

How much of the incident sound is absorbed (a) and scattered (s)

How uniform is the scattered sound (dn)

Uni

form

Diff

usio

n

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

125 160 200 250 320 400 500 630 800 1000 1260 1600 2000 2500 3125 4000

Frequency, Hz

Coe

ffici

ents

s dn a

Amount of scattered sound = [(1-a)s]

CSI Spec: Division 09, Section 09XXX, System Description / Performance Requirements

• Performance RequirementsAbsorption Coefficient: Third-octave band acoustical performance requirements from 100 Hz to 4000 Hz for random incidence sound absorption shall be measured according to ASTM C423 or ISO 354;

Diffusion Coefficient: The normalized random incidence diffusion coefficient shall be the average of measured or calculated directional diffusion coefficients, according to AES-4id-2001 at -60, -30, 0, 30, and 60 degrees.Directional polar responses, which indicate the uniformity of scattering in third-octave bands, for sample and reference reflector, shall be provided to the acoustical consultant for approval.

Scattering Coefficient: The random incidence scattering coefficient shall be measured according to ISO- 17497-1 (Scattering (ISO)) or determined from the average of the measured directional correlation scattering coefficients (Scattering (c)) according to the method of Mommertz [Reference 1.05/E1 and 1.05/E3].

• The random incidence coefficients shall be what are indicated in the table

f (Hz) Diffusion Scattering (ISO) Absorption

100 0.05 0.03 0.28125 -0.01 -0.01 0.22160 0.01 0.00 0.22200 0.00 0.00 0.29250 0.00 0.03 0.29315 0.19 0.03 0.26400 0.24 0.03 0.27500 0.54 0.07 0.33630 0.57 0.17 0.32800 0.57 0.35 0.30

1000 0.54 0.49 0.221300 0.47 0.79 0.191600 0.53 1.00 0.192000 0.46 1.00 0.182500 0.53 1.00 0.183150 0.64 0.87 0.214000 0.62 0.96 0.20

Box-in-BoxThe complete decoupling of floors, walls and ceilings from the building structure to achieve

a high isolation efficiency for airborne & structure-borne noise

Part 2: Acoustic Tools Isolation

Sound Paths

Flanking sound

STC E90/E413 FSTC E336

No Low Frequency Information below 125 Hz

Focus on resonant frequency to control low frequencies

STC

Floor Isolation

Wall Isolation

Ceiling Isolation

Door Isolation

STC 41STC 41--4949 STC 55STC 55

HVAC Options

Part 3: Effective School DesignsClassroomLecture Hall Conference/Meeting Rooms

AuditoriumCeilingWallsPitShells

Music RehearsalMusic Practice

GymatoriumNatatoriumCafeteriasCommon AreasPhysical Plant

SPEECH ROOMSSPEECH ROOMS

What did you say?• The ear / brain processor can fill in a substantial amount of

missing information in music, but requires more detailed information for understanding speech.

• The speech power is delivered in the vowels (a, e, i, o, u and sometimes y) which are predominantly in the frequency range of 250Hz to 500Hz.

• The speech intelligibility is delivered in the consonants (b, c, d, f, g, h, j, k, l, m, n, p, q, r, s, t, v, w), which requires information in the 2,000Hz to 4,000 Hz frequency range.

People who suffer from noise induced hearing loss typically have a 4,000Hz notch, which causes severe degradation of speech intelligibility.

• Why would we want to use ACT or thin fabric wrapped panels that absorb these important frequencies on ceilings of speech rooms and prevents them from fusing with the direct sound and making it louder and more intelligible???

REFLECTION

ABSORPTION DIFFUSION

SpeechIntelligibility

• Classroom

• Lecture Hall

• Conference Room

Speech Acoustic Tools

Effect of early reflections

Speech Intelligibility Quantified1. Word Lists

A series of phonetically tailored words is read and listeners are graded on the % of the words they correctly identify.

2. % ALCONS (Articulation Loss of Consonants) ~ PeutzEquation based calculation factoring in distance, reverberation, room volume, directivity, etc. Below 10% is excellent. Below 15% is good.

3. STI/RASTISpeech Transmission Index correlates intelligibility with the decrease in modulation of the speech signal as it passes through the room. RASTI is a rapid implementation. >0.65 recommended.

4. Early to Total Energy Ratio (Distinctness or D50)The ratio of sound arriving in the first 50 ms to the total sound is often used as a measure of speech clarity. >65% is recommended.

Speech Intelligibility ~ D50

502

050

2

0

% 100 *

ms

p dt

D

p dt∞=∫

∫

Distinctness

Greater the amount of energy arriving before 50 ms after the direct sound the higher the distinctness & the better the speech intelligibility. ( > 65% = Good)

Source

Signal to Noise Ratio

• Many of the problems that arise in poorly designed speech rooms stem from a low Signal to Noise Ratio.

• Signal ~ Direct Sound & Early Reflections (50 ms).

• Noise ~ Reverberation, Occupant Noise, Exterior Noise Intrusion & Noisy MEPF Systems

Signal to Noise ~ Intelligibility

T60 Corrupts Speech Intelligibility

Anechoic

T60 0.8 sec

T60 2 sec

T60 1.3 sec

Courtesy MC2

• Normal adults typically require 0 dB signal-to-noise ratios for high speech intelligibility when listening to simple and familiar speech material for short periods of time.

• An additional 2 dB is needed to compensate for neurological immaturity

• An additional 5 dB is required to compensate for sensorineural and conductive hearing losses

• An additional 5 dB is required for limited English proficiency and language disorders

• An additional 3 dB is required to compensate for the effects of excessive reverberation.

• These additional requirements for classrooms total 15 dB over that of normal adults, or a signal-to-noise ratio of +15 dB.

• We can use the passive acoustics of the architecture to provide some of this needed gain.

Signal to Noise~ Intelligibility

• Most approaches only try to reduce the Noise & often simultaneously decrease the strength of the Signal as well. The result is no net improvement.

• The best approach is to simultaneously increase the signal by providing useful, early, diffuse reflections and decrease the Noise from all sources including reverberation by using appropriately placed Diffsorption.

Signal to Noise~ Intelligibility

ACOUSTICSACOUSTICS

CLASSROOM ~ Basics

Acoustic Goals

1. Quiet room, free from distractions.2. Appropriate Reverberance for Speech

Intelligibility.3. Strong, early, diffuse reflections for Loudness,

Envelopment & Speech Intelligibility.

High Signal to Noise Ratio !

CLASSROOM ~ BasicsWorst Case Scenario(s)

• Room dividers, curtain dividers or single-layer GWB walls.• Common doors and other noise flanking paths (central

clocks, electrical outlets, light switches, etc).• Sliding doors, hollow doors, no doors, doors without

gaskets. • No ceiling (open to floor/roof above).• Sound absorptive ceiling.• No carpet under student seating.• No wall absorption/diffsorption (painted GWB or CMU).• Rooftop HVAC units, VAV/FPB box or perimeter heat unit in

classroom, roof drain pipes or toilet exhaust fan ducts passing through rooms, unlined ducts, return plenum or transfer grilles, air velocities over 500 fpm, air terminals over NC-25, etc.

CLASSROOM ~ BasicsBest Case Scenario(s)

Massive walls (8” CMU or 6” insulated, double-layer GWB)• No noise flanking paths (offset penetrations, ducts/conduits

above corridor ceiling).• Solid core wood doors with gaskets. • Double layer, isolated, insulated GWB ceiling. Diffusion

over center/front part of room. Diffsorption along sides and rear.

• Carpeted floors under student seating. Hard floor in center/front part of room.

• 25-50% wall diffsorption (BAD panels) ~ Consider soffits treated with diffsorption (BAD Panels).

• Maximum NC-25 background noise, HVAC in MERs, duct silencers, lined ductwork, ducted return, VAV/FPB above corridor, air velocities below 500 fpm within 25’ of classroom, NC-20 air terminals.

CLASSROOM ~ Analysis

Ceiling Treatment Options

Diffusion

Reflection

Absorption

Classroom~ Concept ModelReflective Front Wall/CeilingReflective Front Wall/Ceiling Diffusive Ceiling Over Diffusive Ceiling Over

Middle of RoomMiddle of Room

Absorptive Absorptive Perimeter Perimeter CeilingCeiling

Diffsorptive Side/Rear WallsDiffsorptive Side/Rear Walls

The sound pressure The sound pressure level, level, SPLSPL, is rather , is rather lowlowin the purely absorptive in the purely absorptive ceiling, making it difficult ceiling, making it difficult for the speaker to project for the speaker to project causing fatiguecausing fatigue

With the diffusive ceiling, With the diffusive ceiling, SPLSPL is is more uniformmore uniform and and there is there is additional acoustic additional acoustic gaingain raising the level in the raising the level in the classroom and making it classroom and making it easier for the speaker to easier for the speaker to project & students to hearproject & students to hear


Diffusion

Absorption

20-50 ms Early Signal

With the purely With the purely absorptive ceilingabsorptive ceiling, , reflections are reflections are sparsesparse with with minimal sound minimal sound arriving from the arriving from the vertical planevertical plane

With With diffusive diffusive ceilingceiling, reflection , reflection density is greaterdensity is greaterand sound is and sound is arriving uniformly arriving uniformly from all directionsfrom all directions


Diffusion

Absorption

• Diffusive ceilings increase the acoustic level and uniformity of coverage without corrupting the speech intelligibility.

• Increasing the acoustic level increases the learning process by extending the attention span and also addresses hearing acuity and hearing impairment.

• The teacher exerts less energy and experiences less fatigue by not speaking into an acoustic vacuum.

• Energy reaches the students from many directions creating a sense of immersion in the learning experience (surround sound vs mono) for a more intimate, attentive learning experience.

• Diffusion also improves student-student and student-teacher communication (not only teacher to student communication).

CLASSROOM ~ Conclusions

ACOUSTICSACOUSTICS

LECTURE ROOM ~ Basics

Acoustic Goals

1. Appropriate Reverberance for high speech Intelligibility.

2. Good Cross-Room Communication so lecturer and audience can engage in dialogue.

3. Good Support so that lecturer can hear himself.4. Freedom from Flutter and Echoes.5. Freedom from extraneous Noise from occupants

and building systems.


Acoustic Goals

1. Appropriate Reverberance for high speech Intelligibility.

• Room Shape (Rectangular Solid or Fan ~ Avoid Circular)

• Room Volume (150 – 250 cf/seat)• Room Height (Low 10’ – 20’)• Absorptive & Diffusive Finish Materials


Acoustic Goals

2. Good Cross-Room Communication so lecturer and audience can engage in dialogue.

• Low, Sound Diffusive/Reflective Ceiling (or Reflectors)

• AVOID SOUND ABSORPTIVE CEILING!


Acoustic Goals

3. Good Support so that lecturer can hear himself.• Specific wall & ceiling surfaces close to and

facing back at lecturer location.• Sound diffusive rear wall (if less than 35’

away)• Sound diffsorptive rear wall (if greater than

35’ away)• Low, Sound Diffusive/Reflective Ceiling (or

Reflectors)• AVOID SOUND ABSORPTIVE CEILING!• AVOID SOUND ABSORPTIVE REAR

WALL


Acoustic Goals

4. Freedom from Flutter and Echoes.• Room Shaping (Avoid Parallel Reflective

Surfaces)• Diffusive Finish Materials• Acoustic Treatment Location (Avoid

S.P.A.S.)

• Single Plane Absorption Syndrome (SPAS)• Absorptive Ceiling & Absorptive Floor• Reflective Walls• Lecture Hall, Classroom, Natatorium, Gymnasium

• During the same time period, a vertical sound ray is attenuated by almost 30 dB due to absorption, while a horizontal sound ray is hardly attenuated at all.

• Leads to a non-mixing sound field characterized by different reverberation times in the two planes.

• Makes echoes and flutter more audible and problematic.

• Diffusion can be used to correct this problem

LECTURE HALL ~ S.P.A.S.

Lecture Room

Absorption

Specular Reflection

Absorption

Diffsorption

Diffusion

HF Diffusion

LECTURE HALL ~ Example

LECTURE HALL ~ Analysis

2D Diffusion

4” BAD Panels


Reflective Risers

Untreated

T60 > 1.5 sec

Treated

T60 = 0.70 sec


LECTURE HALL ~ Example

Room Shape ~ Rectangular, FanRoom Volume ~ 150 to 250 cf/seat.Low, sound diffusive/reflective ceiling or ceiling reflectors (Not Absorptive)Reflective front wallDiffusive/reflective side walls (below 8’)Diffsorptive side walls (above 8’)Diffsorptive rear wallReflective surfaces close to and facing lecturerMassive boundary construction & quiet building systems

LECTURE ROOM ~ Checklist

ACOUSTICSACOUSTICS

ACT Ceiling ~ Carpeted Floor ~ Untreated Drywall Walls

Conference Room - Small

Diffsorption

2D Diffusion

ACT Ceiling ~ Carpeted Floor ~ Absorptive Panels on Walls

Conference Room

2D Diffusion

1D Diffusion

Conference Room - Analysis

Conference Room - AnalysisTypical Treatment Proper Treatment

ABSORPTION ABSORPTION

DIFFUSION DIFFUSION

Conference Room - Analysis

Typical Treatment Proper TreatmentSPL (dB)

ACOUSTICSACOUSTICS

Acoustical Model

Case 0 ~ No Treatment

ABSORPTION

Case 0 ~ Reverberation

TOO LONG FOR A MULTI-USE AUDITORIUM

GOAL

Case 1 ~ Acoustic Deck

ABSORPTION


GOAL

TOO LONG FOR A MULTI-USE AUDITORIUM

SPL Non-Uniformity

Case 0

Standard Metal Deck

No Treatment or Reflectors

Great Variation & Bad Uniformity

Case 1

‘Acoustic’ Metal Deck

No Other Treatment

Less Variation (Except Rear Seats)

Less Reverberance & More Echoes

Case 2 ~ Reflectors


GOAL

APPROPRIATE FOR A MULTI-USE AUDITORIUM

Case 3 ~ Absorptive Rear Wall

ABSORPTION


GOAL

TOO SHORT FOR A MULTI-USE AUDITORIUM

Case 5 ~ Diffusive Surfaces

DIFFUSION


GOAL

APPROPRIATE FOR A MULTI-USE AUDITORIUM

Rear Wall Treatment

Case 3

Rear Wall Sound ABSORTIVE

No Diffusion


Rear 1/2 of Seating Suffers

Case 4

Rear Wall Sound DIFFUSIVE

No Absorption

Far Less Variation, More Uniform

Rear 1/2 of Seating Benefits


Case 3

Rear Wall Sound ABSORTIVE

No Diffusion

Frontal, Non-Enveloping Sound

Case 4

Rear Wall Sound DIFFUSIVE

No Absorption

Enveloping, Immersive Sound

Forestage Redesign

SPL Uniformity ~ Diffusion

Case 2

Smaller Forestage Reflector

No Diffusion


Case 2B

Larger Forestage Reflector

No Diffusion

Still Some Variation & Nonuniformity

Case 6

Larger Forestage Reflector

Diffusive Surfaces

Very Little Variation & Good Uniformity

SUCCESS !

GOAL

• Appropriate Reverberation Time

• Even Sound Distribution ~ Free From Spatial & Temporal Non-Uniformity

• Enveloping Experience

College of St. Rose

College of St. Rose

Chautauqua Fletcher Hall

Patterson Mill HS

Bethpage HS

Mattituck HS

Harrisburg HS

Academy of the Holy Cross HS

Ben Davis HS

Recital Hall

Farmingdale HS

Lincoln Way HS

Cedarburg HS

Farmingdale HS

ACOUSTICSACOUSTICS

Rutgers University Beyrouth Pit

Cyfair College

ACOUSTICSACOUSTICS

Ceiling Reflectors ~ Diffusive Shape

Kresge Auditorium MIT

Ball State University

Flown Towers and Canopy

Murray Arts Center

1st Baptist Church Eugene

ACOUSTICSACOUSTICS

WOULD YOU INCLUDE THIS IN YOUR PORTFOLIO?

Outdated Band Room Example

Band Room~ Analysis• Untreated

• Treated--Low Frequency Low Frequency ControlControl

--Loudness ControlLoudness Control

--EnsembleEnsemble

--Variable AcousticsVariable Acoustics

Emporia State University

College of St. Rose

Emporia State

Commodores Navy Band

Band Room

ACOUSTICSACOUSTICS

Cleveland Institute of Music

ACOUSTICSACOUSTICS

Cleveland Institute of Music

Distance Learning:Distance Learning:

-- Musical EducationMusical Education

-- Master Classes Master Classes

ACOUSTICSACOUSTICS

GYMNASIUM ~ Basics

Gymnasiums can serve a variety of functions beyond sporting events.

Classes ~ Dances ~ Meetings ~ Plays ~ Concerts

Acoustic Goals1. Adequate Speech Intelligibility2. Controlled Harshness & Loudness3. Low Frequency Absorption4. Prevention of Echoes and Flutter

GYMNASIUM ~ Basics

Acoustic SolutionUpper Wall Diffsorptive Treatment

• Upper Walls (8’ – 20’ Above Floor)• 75% Acoustic CMU (Pigmented, Slotted)• 75% Binary Amplitude Diffsorbor (BAD)

PanelsCeiling/Deck

• Acoustic Metal Deck (NRC 0.75+)• Acoustic Baffles (Hanging Vertically)• Acoustic Ceiling Tile (Durability?)

Acoustic Block

Gym Acoustic Treatment

Acoustic Metal Deck

GYMNASIUM ~ AnalysisCase 1: No Acoustic Treatment• Case 1: 4 s• Roof – Metal Roof Deck• Walls Painted CMU (All)

Case 2: Minimal Acoustic Treatment• Case 2: 3 s• Roof – Acoustic Metal Deck• Walls – Painted CMU

Case 3: Moderate Acoustic Treatment• Case 3: 1.3 s• Roof – Acoustic Metal Deck• Walls – Acoustic CMU (2), Painted CMU (2)

Case 4: Required Acoustic Treatment• Roof - Acoustic Metal Deck• Walls – Acoustic CMU (Upper) Painted CMU• Case 4: 0.9 s

Porter Township HS ~ Example

Zanesville Gymnasium

ACOUSTICSACOUSTICS

Swimming Pools

Ceiling should be 75% Ceiling should be 75% sound absorptive.sound absorptive.

Upper walls should be Upper walls should be 50% sound 50% sound absorptive/diffsorptive.absorptive/diffsorptive.

Swimming Pool

ACOUSTICSACOUSTICS

Cafeterias

Ceiling should Ceiling should be 75% sound be 75% sound absorptive. absorptive.

Walls should be Walls should be 50% sound 50% sound absorptive. absorptive.

ACOUSTICSACOUSTICS

Morgan State University

Elementary School

Public Library

ACOUSTICSACOUSTICS

Northeastern University

ACOUSTICSACOUSTICS

Noise Barriers

Documents

Acoustics RPG Diffusion