acoustical performance criteria

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ANSI S12.60-2002 American National Standard Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools

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AMERICAN NATIONAL STANDARDACOUSTICAL PERFORMANCECRITERIA, DESIGN REQUIREMENTS,AND GUIDELINES FOR SCHOOLS

Accredited Standards Committee S12, Noise

Standards SecretariatAcoustical Society of America35 Pinelawn Road, Suite 114EMelville, NY 11747-3177

ANSI S12.60-2002

AN

SIS1

2.60

-200

2

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AMERICAN NATIONAL STANDARD

Acoustical Performance Criteria,Design Requirements,

and Guidelines for Schools

SecretariatAcoustical Society of America

Approved 26 June 2002American National Standards Institute, Inc.

Abstract

This Standard provides acoustical performance criteria, design requirements, and design guidelines fornew school classrooms and other learning spaces. The standard may be applied when practicable to themajor renovation of existing classrooms. These criteria, requirements, and guidelines are keyed to theacoustical qualities needed to achieve a high degree of speech intelligibility in learning spaces. Designguidelines in informative annexes are intended to aid in conforming to the performance and designrequirements, but do not guarantee conformance. Test procedures are provided in an annex whenconformance to this standard is to be verified.

ANSI S12.60-2002


AMERICAN NATIONAL STANDARDS ON ACOUSTICS

The Acoustical Society of America (ASA) provides the Secretariat for AccreditedStandards Committees S1 on Acoustics, S2 on Mechanical Vibration and Shock,S3 on Bioacoustics, and S12 on Noise. These committees have wide represen-tation from the technical community (manufacturers, consumers, trade associa-tions, general-interest and government representatives). The standards are pub-lished by the Acoustical Society of America through the American Institute ofPhysics as American National Standards after approval by their respective Stan-dards Committees and the American National Standards Institute.

These standards are developed and published as a public service to providestandards useful to the public, industry, and consumers, and to Federal, State, andlocal governments.

Each of the accredited Standards Committees, operating in accordance with pro-cedures approved by American National Standards Institute (ANSI), is responsiblefor developing, voting upon, and maintaining or revising its own Standards. TheASA Standards Secretariat administers Committee organization and activity andprovides liaison between the Accredited Standards Committees and ANSI. Afterthe Standards have been produced and adopted by the Accredited StandardsCommittees, and approved as American National Standards by ANSI, the ASAStandards Secretariat arranges for their publication and distribution.

An American National Standard implies a consensus of those substantially con-cerned with its scope and provisions. Consensus is established when, in thejudgment of the ANSI Board of Standards Review, substantial agreement hasbeen reached by directly and materially affected interests. Substantial agreementmeans much more than a simple majority, but not necessarily unanimity. Consen-sus requires that all views and objections be considered and that a concertedeffort be made towards their resolution.

The use of American National Standards is completely voluntary. Their existencedoes not in any respect preclude anyone, whether he or she has approved theStandards or not, from manufacturing, marketing, purchasing, or using products,processes, or procedures not conforming to the Standards.NOTICE: This American National Standard may be revised or withdrawn at anytime. The procedures of the American National Standards Institute require thataction be taken periodically to reaffirm, revise, or withdraw this Standard.

Standards SecretariatAcoustical Society of America35 Pinelawn Road, Suite 114 EMelville, New York 11747-3177Telephone: 1 1 631 390 0215Telefax: 11 631 390 0217E-mail: [email protected]

2002 by Acoustical Society of America. This standard may not be reproduced in whole orin part in any form for sale, promotion, or any commercial purpose, or any purpose notfalling within the provisions of the Copyright Act of 1976, without prior written permission ofthe publisher. For permission, address a request to the Standards Secretariat of the Acous-tical Society of America.


ContentsPage

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Scope, purpose and applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Acoustical performance criteria and noise isolation design

requirements and guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

AnnexesA Rationale for acoustical performance criteria . . . . . . . . . . . . . . . . . . 10B Design guidelines for noise control for building services,

utilities, and instructional equipment . . . . . . . . . . . . . . . . . . . . . . . . . . 14C Design guidelines for controlling reverberation in classrooms

and other learning spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17D Design guidelines for noise isolation . . . . . . . . . . . . . . . . . . . . . . . . . 23E Good architectural practices and procedures to verify

conformance to this standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27F Potential conflicts between the acoustical requirements of this

standard and indoor air quality (IAQ) and multiple chemicalsensitivity (MCS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

G Cautionary remarks on using supplemental descriptors forevaluating noise in classrooms and other learning spaces . . . . . . 35

Tables1 Maximum A-weighted steady background noise levels and

maximum reverberation times in unoccupied, furnishedlearning spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Minimum STC ratings required for single or composite wall,floor-ceiling, and roof-ceiling assemblies that separate anenclosed core learning space from an adjacent space . . . . . . . . . 7

3 Minimum STC ratings recommended for single or composite wall,floor-ceiling and roof-ceiling assemblies separating an ancillaryspace from an adjacent space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

C.1 Minimum surface area of acoustical treatment for differentsound absorption coefficients, ceiling heights, and reverberationtimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

D.1 Approximate difference between the minimum STC ratingrequired for building envelope components and the requiredoutdoor-to-indoor noise level reduction . . . . . . . . . . . . . . . . . . . . . . . 25

D.2 Correction data for estimating the STC rating of a two-elementcomposite building assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

i


Foreword

[This foreword is for information only and is not an integral part of AmericanNational Standard Acoustical Performance Criteria, Design Requirements, andGuidelines for Schools.]This standard contains 7 annexes.This standard was developed under the jurisdiction of Accredited Standards Com-mittee S12, Noise, which has the following scope:

Standards, specifications, and terminology in the field of acoustical noise pertainingto methods of measurement, evaluation, and control, including biological safety, tol-erance, and comfort, and physical acoustics as related to environmental and occu-pational noise.

At the time this standard was submitted to Accredited Standards Committee S12,Noise, for final approval, the membership was as follows:

P.D. Schomer, ChairmanR.D. Hellweg, Vice Chairman

S.B. Blaeser, Secretary

Abbot Laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D. WaltonB. Muto (Alt.)

Acoustical Society of America . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B.M. BrooksW.J. Galloway (Alt.)

Aearo Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E.H. BergerAir-conditioning and Refrigeration Institute (ARI) . . . . . . . . . . . . . . . . R. Seel

M. Darbeau (Alt.)Aluminum Company of America (ALCOA) . . . . . . . . . . . . . . . . . . . . . . . W.D. GallagherAmerican Academy of Otolaryngology,Head and Neck Surgery, Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R.A. Dobie

L.A. Michael (Alt.)American College of Occupational Medicine. . . . . . . . . . . . . . . . . . . . . P.J. Brownson

J. Sataloff (Alt.)American Industrial Hygiene Association . . . . . . . . . . . . . . . . . . . . . . . . D. Driscoll

J. Banach (Alt.)American Otological Society . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R.F. NauntonAmerican Society of Heating, Refrigeration, andAir-Conditioning Engineers (ASHRAE) . . . . . . . . . . . . . . . . . . . . . . . . . H.S. Pei

C. Ramspeck (Alt.)American Speech-Hearing-Language Association (ASHA) . . . . . . . . J.D. Royster

R. Levinson (Alt.)Audio Engineering Society, Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M.R. Chial

D. Queen (Alt.)Bruel & Kjaer Instruments, Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. Alexander

J. Chou (Alt.)Caterpillar, Inc.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K.G. Meitl

D.G. Roley (Alt.)Compressed Air and Gas Institute (CAGI) . . . . . . . . . . . . . . . . . . . . . . . J.H. Addington

D.R. Bookshar (Alt.)Council for Accreditation in OccupationalHearing Conservation (CAOHC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R. Danielson

E.H. Berger (Alt.)Howard Leight Industries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V. LarsonIndustrial Safety Equipment Association . . . . . . . . . . . . . . . . . . . . . . . . J. Birkner

J.C. Bradley (Alt.)Information Technology Industry Council (ITIC) . . . . . . . . . . . . . . . . . . R.D. Hellweg

W.H. Johnson (Alt.)James, Anderson & Associates (JAA) . . . . . . . . . . . . . . . . . . . . . . . . . . L.D. Hager

R.R. Anderson (Alt).iii


Larson-Davis, Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L. DavisL. Harbaugh (Alt.)

Lucent Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. MottahedD. Quinlan (Alt.)

National Council of Acoustical Consultants . . . . . . . . . . . . . . . . . . . . . . J. ErdreichNational Electrical Manufacturers Association (NEMA) . . . . . . . . . . . . D. RawlingsNational Hearing Conservation Association (NHCA) . . . . . . . . . . . . . . K.L. MichaelNorth American Insulation Manufacturers Association. . . . . . . . . . . . . R. Godfrey

R. Moulder (Alt.)Power Tool Institute, Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Rescigno

J. Nosko (Alt.)U.S. Department of the Air Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R.L. McKinleyU.S. Army Aeromedical Research Lab . . . . . . . . . . . . . . . . . . . . . . . . . W. Ahroon

D. Ostler (Alt.)U.S. Army Center for Health Promotion and Preventive Medicine . . G.A. Luz

W. A. Russell (Alt.)U.S. Army Construction Engineering Research Laboratories (USA-

CERL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L. PaterU.S. Army Human Research & Engineering Directorate . . . . . . . . . . J. Kalb

T.R. Letowski (Alt.)U.S. Naval Surface Warfare Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . S.A. Fisher

J.M. Niemiec (Alt.)U.S. Department of Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Konheim

Individual Experts of Accredited Standards Committee S12, Noise, were:P.K. BaadeR.W. BensonL.L. BeranekE.H. BergerS.H.P. BlyB.M. Brooks

K.M. EldredL.S. FinegoldW.J. GallowayR.K. HillquistD.L. JohnsonW.W. LangG.C. Maling, Jr.

A.H. MarshJ. PopeJ.D. RoysterP.D. SchomerJ.P. SeilerL.C. Sutherland

W.R. ThorntonH.E. von GierkeL.A. WilberG.E. WinzerG.S.K. WongR.W. Young

Working Group S12-42, Classroom Acoustics, which assisted Accredited Stan-dards Committee S12, Noise, in the preparation of this standard, had the followingmembership:

D. Lubman and L.C. Sutherland, Co-Chairmen

K.L. AndersonR.E. ApfelJ.S. BradleyB.M. BrooksD.C. BruckA.J. CampanellaR.C. CoffeenD. CollingsC.C. CrandellT.J. DuBoisG. EhrlichS.L. EhrlichJ. ErdreichD. Fagen

R.D. GodfreyJ.J.C. GouldW.H. HannonR.D. HellwegM.R. HodgsonK.A. HooverS. InglisC.D. JohnsonD.L. JohnsonH.F. KingsburyJ.G. LillyJ. LyonsH.L. MerckR. Moulder

P.B. NelsonM.T. NixonJ. OlsonS.W. PayneK.S. PearsonsR.J. PeppinJ. PopeD. QueenR. RandallL. ReddenS.I. RothK.P. RoyM.E. Schaffer

A. SeltzN.T. ShadeL.L. SemeskyG.W. SiebeinJ.J. SmaldinoS.D. SoliD.L. SorkinN.D. StewartL. ThibaultB.D. TinianovE.A. WetherillS.J. WoodheadW.A. Yost

Suggestions for the improvement of this standard are welcome. They should bemade in writing to Accredited Standards Committee S12, Noise, in care of theStandards Secretariat, Acoustical Society of America, 35 Pinelawn Road, Suite114E, Melville, New York 11747. Telephone: 11 631 390 0215; FAX: 11 631 3900217; e-mail: [email protected]

iv


American National Standard

ACOUSTICALPERFORMANCECRITERIA, DESIGNREQUIREMENTS, ANDGUIDELINES FORSCHOOLS0 Introduction

Good acoustical qualities are essential in class-rooms and other learning spaces in which speechcommunication is an important part of the learningprocess. Excessive background noise or rever-beration in such spaces interferes with speechcommunication and thus presents an acousticalbarrier to learning. With good classroom acoustics,learning is easier, deeper, more sustained, andless fatiguing. Teaching should be more effectiveand less stressful with good acoustical character-istics in a classroom. There can be more verbalinteraction and less repetition between teacherand students when spoken words are clearly un-derstood. Although all those in a classroom, in-cluding teachers and adult learners, will benefit,special beneficiaries are young children and per-sons with hearing, language, speech, attentiondeficit, or learning disabilities. As discussed furtherin annex A, conformance to this standard will im-prove the quality of education by eliminatingacoustical barriers for all students and teachers,including those with communication disabilities.Good design and attention to detail throughout theconstruction or renovation process can ensureconformance to the requirements of this standard.

1 Scope, purpose, and applications1.1 Scope1.1.1 This standard provides acoustical perfor-mance criteria and design requirements for class-rooms and other learning spaces. Annexes are in-cluded to provide information on good design andconstruction practices, installation methods, andoptional procedures to demonstrate conformanceto the acoustical performance and design require-ments of this standard. This standard seeks to pro-

vide design flexibility without compromising thegoal of obtaining adequate speech intelligibility forall students and teachers in classrooms and learn-ing spaces within the scope of this standard.1.1.2 Acoustical performance criteria are specifiedin this standard by limits on maximum one-hourA-weighted and C-weighted background noise lev-els and limits on maximum reverberation times. Anobjective of these performance criteria is toachieve a level of speech that is sufficiently highrelative to the background noise level for listenersthroughout the classroom or learning space. How-ever, a requirement for the relative difference be-tween speech levels and levels of backgroundnoise, usually referred to as the signal-to-noise ra-tio, is not within the scope of this standard.1.1.3 The control of background noise levels inthis standard is achieved, in part, by specifying theminimum noise isolation for school building ele-ments. Noise isolation requirements are applicableto the following two types of intrusive noise.

Noise that intrudes into the classroom orlearning space from sources outside of theschool building envelope. These noise sourcesinclude vehicular traffic, aircraft, industrialplants, and activity in schoolyards or fromgrounds maintenance. (Schools usually cancontrol only the schoolyard and grounds-main-tenance noise sources. However, when a newschool site is under consideration, sound fromcommercial, industrial and transportation noisesources can be taken into account.) Noise that originates within the school build-ing and intrudes into the classroom throughclassroom walls and partitions, floor-ceiling as-semblies and ventilation systems. Interior noisesources can be isolated through the proper de-sign and construction of the school building andby noise control measures applied to the build-ing services and utilities.

1.1.4 This standard does not apply to noise gen-erated within a classroom by its occupants. Occu-pant-generated noise sources include voices andthe sounds of classroom activities such as themoving of chairs. Furthermore, this standard doesnot apply to the noise from portable or permanentbuilt-in equipment used during the course of in-struction, such as audiovisual equipment and com-puters. However, the background noise generatedby occupants and instructional equipment can se-riously degrade communication or speech intelligi-

AMERICAN NATIONAL STANDARD ANSI S12.60-2002

1 2002 Acoustical Society of America


bility in learning spaces. Recommendations aregiven in B5 in annex B for noise control of instruc-tional equipment. Recommendations for back-ground noise assessment procedures are given inE3.2.1 in annex E for such equipment. The teachercan reduce classroom activity noise directlythrough appropriate controls. This activity noisecan also be reduced indirectly in classrooms withacoustical qualities that conform to this standardsince a quiet classroom with low reverberationtends inherently to encourage children to lower thelevel of their voices and the sounds of their activity.1.1.5 The following annexes are provided to sup-port this standard.

Annex A: Rationale for the acoustical perfor-mance criteria in this standard. (Informative) Annex B: Design guidelines for noise controlfor building services, utilities, and instructionalequipment. (Informative) Annex C: Design guidelines for controlling re-verberation in classrooms and other learningspaces. (Informative) Annex D: Design guidelines for noise isolationbetween adjacent learning spaces within aschool building and noise isolation by the build-ing facade. (Informative) Annex E: Good architectural practices andprocedures to verify conformance to the stan-dard. (Normative but Informative if conformanceis not to be verified.) Annex F: Potential conflict between theacoustical requirements of this standard and in-door air quality (IAQ) and multiple chemicalsensitivity (MCS). (Informative) Annex G: Cautionary remarks on usingsupplemental descriptors for evaluating noise inclassrooms and other learning spaces. (Infor-mative)

1.2 Purpose

This standard is intended to help school plannersand designers provide the acoustical qualities nec-essary for good speech communication betweenstudents and teachers in classrooms and otherlearning spaces without the use of electronic am-plification systems.

1.3 Applications1.3.1 This standard applies to classrooms andother core learning spaces of small-to-moderatesize with volumes not exceeding 566 m3 (20 000ft3) and to ancillary learning spaces of any volume.

Core learning spaces larger than the above vol-ume limit shall be considered ancillary spaces forpurposes of this standard. The standard does notapply to special-purpose classrooms, teleconfer-encing rooms, special education rooms, such asthose for severely acoustically-challenged stu-dents or other spaces, such as large auditoria thathave unique or more stringent acoustical require-ments. Conformance to the requirements of thisstandard should be considered to be a minimumgoal for the acoustical qualities of such spaces,excluding auditoria. The standard does not providerecommendations for electronic amplification or forelectronic aids for persons with hearing impair-ment.

1.3.2 The acoustical performance criteria and de-sign requirements of this standard apply during thedesign and construction of all new classrooms orlearning spaces of small-to-moderate size asspecified in 1.3.1. As far as is practicable, theseacoustical performance criteria and design re-quirements also apply during the design and re-construction of all renovated classrooms andlearning spaces. However, the noise reduction andreverberation control principles in this standardalso apply to larger classrooms or learning spaces.Thus, while this standard does not necessarily ap-ply to all college and university classrooms or lec-ture halls, business or professional educational in-stitutions or other adult education centers,acoustical performance criteria and design re-quirements similar to those in this standard maystill pertain to such applications. Appropriate appli-cation of this standard to such alternative learningspaces is encouraged.1.3.3 This standard is intended for use by schoolbuilding specialists, educators, and parents. Theinformation in annexes B, C, and D is intended fordirect application by school design professionalsincluding architects.

2 Normative references

The following standards contain provisions that,through reference in this text, constitute provisionsof this American National Standard. At the time ofapproval of this standard by the American NationalStandards Institute, Inc. (ANSI), the editions indi-cated were valid. Because standards are revisedfrom time to time, users should consult the latestrevision approved by the American National Stan-dards Institute (ANSI), International Electrotechni-cal Commission (IEC), and the American Society

ANSI S12.60-2002



for Testing and Materials (now called ASTM Inter-national). For the purposes of this standard, theuse of the latest revision of a referenced standardis not mandatory. Information on recent editions isavailable from the ASA Standards Secretariat andASTM International.ANSI S1.1-1994 (R1999), American NationalStandard Acoustical Terminology [Web Site - http://asa.aip.org].ANSI S1.4-1983 (R2001), American NationalStandard for Sound Level Meters.ASTM E336-97, Standard Test Method for Mea-surement of Airborne Sound Insulation in Build-ings. [Web site - http://www.astm.org].ASTM E413-87 (1999), Standard Classification forRating Sound Insulation.ASTM E989-89 (1999), Standard Classification forDetermination of Impact Insulation Class (IIC).ASTM E1007-97, Standard Test Method for FieldMeasurement of Tapping Machine Impact SoundTransmission Through Floor-Ceiling Assembliesand Associated Support Structures.IEC 61672-1, Electroacoustics Sound levelmeters Part 1: Specifications [Web site - http://www.iec.ch].

3 Definitions

The following definitions apply for the purposes ofthis standard.3.1 General terms

3.1.1 classrooms and other learning spaces.Locations within buildings where students as-semble for educational purposes.3.1.1.1 core learning spaces. Spaces for educa-tional activities where the primary functions areteaching and learning and where good speechcommunication is critical to a students academicachievement. These spaces include, but are notlimited to, classrooms, (enclosed or open plan),instructional pods or activity areas, group instruc-tion rooms, conference rooms, libraries, offices,speech clinics, offices used for educational pur-poses and music rooms for instruction, practiceand performance.3.1.1.2 ancillary learning spaces. Spaces wheregood communication is important to a studentseducational progress but for which the primaryeducational functions are informal learning, social

interaction or similar activity other than formal in-struction. These areas include, but are not limitedto, corridors, cafeterias, gymnasia, and indoorswimming pools.3.1.2 acoustical privacy. Pertains to the acousti-cal attenuation between spaces that is needed toprevent conversation in one space from being un-derstood in an adjacent space.3.1.3 conforming learning space. Any class-room or other learning space for which the acous-tical performance criteria and design requirementsconform to this standard.

3.2 Terms relating to acoustical performanceand designThe following terms are defined in a simplifiedform. Complete technical definitions are providedin ANSI S1.1.3.2.1 noise level or sound level. Generic termsemployed interchangeably throughout this stan-dard to represent the frequency-weighted soundpressure level of an airborne sound. This descrip-tor is used to express the magnitude of a sound ina manner related to how the ear perceives thismagnitude. Noise level or sound level is expressedin decibels, unit symbol dB.

3.2.1.1 A-weighted sound level. Sound pressurelevel measured with a conventional frequencyweighting that roughly approximates how the hu-man ear hears different frequency components ofsounds at typical listening levels for speech. TheA-weighting (see ANSI S1.4 or IEC 61672-1) at-tenuates the low-frequency (or low-pitch) contentof a sound. A-weighted sound level is expressed indecibels, unit symbol dB.

3.2.1.2 C-weighted sound level. Sound pressurelevel measured with a conventional frequencyweighting (see ANSI S1.4 or IEC 61672-1) thatdoes not significantly attenuate the low- frequency(or low-pitch) content of a sound. C-weightedsound level is expressed in decibels, unit symboldB.

3.2.1.3 one-hour-average A-weighted or C-weightedsound level. Level of the time- mean-squareA-weighted or C-weighted sound pressure aver-aged over a one-hour period. One-hour- averagesound level is expressed in decibels, unit symboldB.3.2.1.4 yearly average day-night average soundlevel. Level of the time-mean-square A-weighted

ANSI S12.60-2002



sound pressure averaged over a one-year periodwith 10 dB added to sound levels occurring in eachnighttime period from 22:00 hours to 07:00 hours.Yearly average day-night average sound level isexpressed in decibels, unit symbol dB.3.2.2 background noise level. Sound in a fur-nished, unoccupied learning space, includingsounds from outdoors, building services and utili-ties operating at their maximum levels. For the pur-poses of this standard, this excludes sound gen-erated by people within the building or soundgenerated by temporary or permanent instruc-tional equipment.3.2.2.1 steady background noise. Noise frombuilding services and utilities and from outdoornoise sources that is fairly constant over time.3.2.2.2 unsteady background noise. Time vary-ing noise from transportation sources, such as air-craft, vehicle traffic or from other time varying out-door or indoor noise sources. Unsteadybackground noise varies substantially over time.3.2.3 reverberation. An acoustical phenomenonthat occurs in an enclosed space, such as a class-room, when sound persists in that space as a re-sult of repeated reflection or scattering from sur-faces enclosing the space or objects in the space,such as chairs or cabinets.3.2.3.1 reverberation time. A measure of theamount of reverberation in a space and equal tothe time required for the level of a steady sound todecay by 60 dB after it has been turned off. Thedecay rate depends on the amount of sound ab-sorption in a room, the room geometry, and thefrequency of the sound. Reverberation time is ex-pressed in seconds, unit symbol s.3.2.4 sound absorption and reflection. Acousti-cal phenomena that occur whenever sound strikesa surface. Absorbed sound is the portion of thesound energy striking the surface that is not re-turned as sound energy. Reflected sound is theremaining portion that bounces off the surface.The magnitude of the reflected sound in a room isdetermined by the amount of sound absorption atthe surfaces, the room geometry, and the fre-quency of the sound. As distance from a soundsource in a classroom increases, the sound is in-creasingly dominated by reflected sound.3.2.4.1 sound absorption coefficient. A mea-sure of the ability of a material to absorb soundand equal to the ratio of the intensity of the ab-

sorbed sound to the intensity of the incident sound.The sound absorption coefficient of a material nor-mally varies with frequency. It ranges from about0.2 to about 1.0 for sound-absorbing materials, toless than 0.05 for a smooth, painted concrete floor.Sound absorption coefficients measured in a labo-ratory (that is, in a reverberation room) can belarger than 1.0 because of test method and samplesize effects.

3.2.5 acoustic isolation. A measure of the de-crease in sound level (attenuation) when soundpasses from one room to another, such as fromone side of a wall to the other side. The passage ofsound may be via an airborne path or via a struc-tureborne path.3.2.5.1 attenuation of airborne sound. Attenua-tion of sound passing through walls or ceilings,between spaces within a building, or through roofsor external walls. The attenuation of airbornesound depends on the sound reduction throughthese elements, on their size, on sound leakagearound their periphery, on the sound absorption inthe receiving space, and on the frequency of thesound.3.2.5.2 sound transmission class. Single num-ber rating for the acoustic attenuation of airbornesound passing through a partition or any otherbuilding element such as a wall, roof, or door asmeasured in an acoustical testing laboratory fol-lowing accepted industry practice, abbreviationSTC. A higher STC rating provides more soundattenuation through a partition.3.2.5.3 noise isolation class. Single number rat-ing of the noise isolation between two enclosedspaces that are acoustically connected by one ormore paths, abbreviation NIC. The rating is de-rived from the difference in sound levels betweentwo spaces. A higher NIC rating provides morenoise isolation between the two spaces.3.2.5.4 impact insulation class. Single numberrating for the attenuation, measured in an acousti-cal testing laboratory, of structureborne soundthrough floor or floor-ceiling assemblies from floorimpacts into the space below, abbreviation IIC. Ahigher IIC rating provides more impact sound at-tenuation into the space below.3.2.5.5 field impact insulation class. Singlenumber rating of the structureborne noise isolationprovided by a floor or floor-ceiling assembly,abbreviation FIIC. The rating is derived from

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the sound levels measured in the receivingroom when a standard tapping machine is operat-ing on the floor assembly in the source roomabove. The higher the FIIC rating, the morethe impact noise isolation between the twospaces.

4 Acoustical performance criteria andnoise isolation design requirements andguidelines4.1 Introduction

Acoustical performance criteria and design re-quirements are contained in the following sub-clauses. The performance criteria shall apply toclassrooms and other core learning spaces and toancillary learning spaces. For purposes of thisstandard it shall be assumed that the learningspaces are furnished consistent with their use andthe building is unoccupied with doors and windowsclosed. Acoustical design requirements for mini-mum noise isolation apply only to fully enclosedclassrooms and learning spaces.

4.2 Performance criteria for background noiseand reverberation time

The one-hour-average A-weighted steady back-ground noise level and the reverberation timesshall not exceed the limits specified in table 1. Thelimits for the background noise shall apply for thefollowing conditions:1) for the noisiest continuous one-hour period dur-ing times when learning activities take place;2) exterior and interior noise sources are operatingsimultaneously;3) interior sources are operating as defined in4.3.2; and4) portable and permanent (built-in) instructionalequipment, such as computers and audio-visualequipment, are turned off.While designing to conform to both acoustical per-formance criteria in table 1 is required, conform-ance to the background noise level criterion is themore important of the two. When optional conform-ance testing is carried out, the tolerances specifiedin 4.7 reflect this relative importance.

Table 1 Maximum A-weighted steady background noise levels and maximum reverberation times inunoccupied, furnished learning spaces

Learning spacea) Maximum one-hour-average A-weightedsteady backgroundnoise levelb,c) dB

Maximum reverberation timefor sound pressure levels in octavebands with midband frequencies of500, 1000, and 2000 Hz s

Core learning space with enclosedvolume , 283 m3 (, 10 000 ft3)

35 0.6

Core learning space with enclosed volume. 283 m3 and < 566 m3 (. 10 000 ft3and < 20 000 ft3)

35 0.7

Core learning spaces with enclosedvolumes . 566 m3 (20 000 ft3)and all ancillary learning spaces

40d) e)

a) See 3.1.1.1 and 3.1.1.2 for definitions of core and ancillary learning spaces.b) See 4.3.1 for limits on unsteady (time varying) background noise levels.c) See 4.3.2 for other limits on background noise from building services and utilities including C-weighted steady

background noise levels.d) When corridors are used solely for conveyance of occupants within the school building and structured learning

activities do not occur, the A-weighted steady background noise level limit for such corridors may be increased to 45dB. The use of corridors for formal learning purposes should be avoided.

e) See C3.3 in annex C for recommendations on control of reverberation in these spaces.

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4.3 Background noise levels4.3.1 Unsteady background noise from trans-portation noise sources. School facilities shouldbe sited and designed to limit the noise levels in-side learning spaces from transportation noisesources, such as aircraft, road vehicles and trains.(See D2.3 in annex D for further guidance on out-door-indoor noise isolation and school siting.)The limits on A-weighted background noise levelsin table 1 shall be increased by 5 dB when thenoisiest hour is dominated by transportation noiseand the following conditions apply to theA-weighted SLOW time-weighted backgroundnoise level. For core learning spaces with en-closed volumes not greater than 566 m3 (20 000ft3), this level does not exceed 40 dB for more than10% of this noisiest hour. For core learning spaceswith enclosed volumes greater than 566 m3 (20000 ft3) and for ancillary learning spaces, this leveldoes not exceed 45 dB for more than 10% of thisnoisiest hour. (See E3.7.2 in annex E for a mea-surement method for this evaluation.)4.3.2 Background noise from building servicesand utilities. Steady background noise fromHVAC systems and other building services andutilities operating simultaneously shall conform tothe requirements of table 1 for all operating modes(for example, cooling, heating, ventilating, and de-humidifying) and at the maximum operating condi-tions (for example, maximum fan speed with alllights on). Unsteady background noise levels fromplumbing systems (for example, toilets and bath-ing rooms) operating at their noisiest condition,shall also conform to the limits in table 1 taking intoconsideration their normally limited operating timewithin any one hour. (See annex B for guidelineson control of noise from HVAC systems, buildingservices, and utilities.)4.3.2.1 Limits on steady C-weighted back-ground noise levels from building servicesand utilities. The maximum one-hour-average C-weighted steady background noise levels from thecombination of HVAC systems, lighting, and otherbuilding services and utilities operating simulta-neously shall not exceed the limits on A-weightedsteady background noise levels in table 1 by morethan 20 dB.4.3.2.2 Limits on disturbing sounds from build-ing services and utilities. Disturbing sounds,such as rumble, hum, buzz, whine, hiss, or whistle,from HVAC systems and other building services

and utilities shall be controlled so as to not inter-fere with speech communication or be distractingor annoying to the occupants of the learningspaces.4.3.2.3 Limits on time-varying noise levels frombuilding services and utilities. The A-frequency-weighted and SLOW time-weighted noise level atany usable location in a room, from HVAC systemsand other building services operating as specifiedin 4.3.2 shall not vary by more than 3 dB duringany 5-s period. This shall be measured with asound level meter conforming to at least the Type2 requirements of ANSI S1.4 or the class 2 re-quirements of IEC 61672-1. Such time-varyingnoise shall be considered to be caused by thebuilding systems and services, unless the noise isclearly recognized as being produced by transpor-tation noise sources, such as road traffic or air-craft, addressed in 4.3.1.4.3.3 Background noise from instructionalequipment. For this standard, noise from instruc-tional equipment is not included in the steadybackground noise. However, control of such noise,especially that from permanent built-in instruc-tional equipment, should be carefully addressed inthe planning stages for new and renovatedschools. (See B5 in annex B for guidance on ap-plicable noise control measures for such instruc-tional equipment.)

4.4 Reverberation times

The maximum allowable reverberation times in un-occupied, furnished core learning spaces arespecified in table 1 for core learning spaces withenclosed volumes of not more than 566 m3 (20000 ft3). Design guidelines for controlling rever-beration time in learning spaces of all sizes and forselection and proper certification for any acousticalmaterials applied to control this reverberation arepresented in annex C.

4.5 Noise isolation design

The first and most cost effective step in achievinggood noise isolation between learning spaces andother spaces in a school is accomplished in thefacility planning stage. This includes optimizing thelocation of noisy spaces and activities to protectsensitive learning spaces. Where this is not pos-sible, adequate noise isolation is needed.4.5.1 Need for noise isolation. The acousticalperformance criteria for background noise levels in

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4.2 and 4.3 apply to unoccupied facilities. How-ever, in occupied facilities, activity noises gener-ated in one space can be transmitted throughwalls, floors, ceilings, and doors to adjacent learn-ing spaces, thus contributing to the overall back-ground noise level in those spaces. Adequatesound isolation is required to limit noise transmis-sion between core learning spaces and adjacentspaces in occupied facilities. The minimum STCratings of table 2 and table 3 are intended to pro-vide this noise isolation for normal activities in ad-joining spaces.Certain educational styles (such as open plan andgroup learning) intentionally avoid the use of fullenclosures between learning groups. Sometimes,partial height sound barriers or no barriers at allseparate adjacent learning groups. Adequatenoise isolation between adjacent learning groupscannot be assured unless each learning group isfully enclosed by ceiling-height sound barriers. Be-cause of the inherent low noise isolation, partiallyenclosed or unenclosed learning spaces are notrecommended when good speech communicationis desired.In occupied multistory educational facilities, thetransmission of impact noise through the floor ofthe room above to the learning space below alsocontributes to the overall background noise level.

To limit impact noise disturbances in learningspaces, this standard also provides minimum im-pact insulation class (IIC) design requirements forthe floor-ceiling assemblies above learning spacesfor multistory educational facilities.

As discussed further in D1 in annex D, the noiseisolation requirements of this standard are similarin concept to those in existing national and inter-national building codes.4.5.2 Noise isolation design requirements. Inthis standard, noise isolation is specified by theminimum values for the STC and IIC ratings forsingle and composite building elements that mayprovide acceptable noise isolation for learningspaces. Selection of these minimum ratings,achieved during architectural design, is the basisfor limiting the transmission of background noisefrom external and interior sources into an enclosedlearning space. After construction, a field mea-surement may be made to verify the noise isolationachieved [see 4.6 (3)].When high noise isolation is required, as for musicrooms, flanking of sound along common floors,walls, and roofs can become a limiting factor un-less controlled with proper breaks in sound trans-mission paths or other similar treatments. Thereare many publications that provide details on de-

Table 2 Minimum STC ratings required for single or composite wall, floor-ceiling, and roof-ceilingassemblies that separate an enclosed core learning space from an adjacent space

Adjacent spaceOther enclosed or open

plan core learningspace, speech clinic,health care room andoutdoorsc)

Common use and publicuse toilet room andbathing room

Corridor,a)staircase, office orconference rooma,b)

Music room, mechanicalequipment room,d)cafeteria, gymnasium,and indoor swimmingpool

50 53 45 60

a) For corridor, office, or conference room walls containing doors, the basic wall, exclusive of the door, shall have anSTC rating as shown in the appropriate column in this table. The entrance door shall conform to the requirementsof 4.5.5.

b) When the need for acoustical privacy is critical, the minimum STC rating of the partitions around an office orconference room shall be increased to 50.

c) An STC rating of 50 is the minimum for the exterior walls and roofs of a core learning space. However, this ratingdoes not ensure conformance to the background noise limits in table 1 for noise from major outdoor noise sources.See D2.3 in annex D for further guidance on the selection of appropriate STC ratings.

d) When the adjacent space is a mechanical equipment room containing fans circulating 140 m3/min. (5000 ft3 /min.)or more, the minimum STC rating shall be 60. When the fan circulation is less than this rate, the STC rating may beas low as 45 providing the maximum A-weighted steady background noise level in the adjacent core learning spacedoes not exceed 35 dB. The minimum STC rating shall include the effect of entry door(s) into the mechanicalequipment room.

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sign and construction of separating partitions thatmay achieve the required STC ratings. Annex Dprovides guidelines and references for such noiseisolation design and construction.

4.5.3 Sound transmission class STC ratings4.5.3.1 Core learning spaces. The minimum STCratings in table 2 shall be employed for the acous-tical design of wall, floor-ceiling and roof assem-blies that separate enclosed or open plan corelearning spaces from adjacent spaces. When theassembly includes two or more elements, such asdoors or windows, the STC of this composite as-sembly also shall conform to the requirements oftable 2.

Composite assemblies are walls, floor-ceiling androof-ceiling constructions composed of more thanone element (for example, a wall with a door, win-dow, or penetrations by HVAC ducts or other ser-vices). (See NOTE a) to table 2 for special require-ments for doors in corridor, office or conferenceroom walls.)Walls and floor-ceiling assemblies may not main-tain their design STC rating if penetrations oropenings for piping, electrical devices, recessed

cabinets, soffits, or heating, ventilating or exhaustducts are unsealed. For this reason, all penetra-tions in sound-rated partitions shall be sealed andtreated to maintain the required ratings. The STCrating requirements of table 2 shall also be em-ployed for the design of temporary partitions thatsubdivide a learning space.4.5.3.2 Ancillary learning spaces. Recommen-dations are given in table 3 for STC ratings forpartitions (that is, walls and floor-ceiling assem-blies) that enclose an ancillary learning space orthat separate two ancillary spaces. When the par-tition includes two or more elements, such asdoors, windows, or penetrations of the partition forHVAC ducts or other services, the STC of thiscomposite construction also should conform to therecommendations of table 3.

4.5.4 Composite partitions. The required mini-mum STC ratings in table 2 apply to single or com-posite partitions. Basic wall assemblies (exceptthose identified in NOTE a) for table 2) which con-tain doors or windows with STC ratings less thanthose given in table 2, will require higher STC rat-ings to conform to the required minimum STC rat-ings of the composite construction. This design

Table 3 Minimum STC ratings recommended for single or composite wall, floor-ceiling and roof-ceiling assemblies separating an ancillary space from an adjacent space

Adjacent spaceReceiving ancillaryLearning space

Corridor,a)staircase, commonuse and public usetoilet and bathingroomb)

Music room Office orconferencerooma)

Outdoorse) Mechanicalequipment room, f)cafeteria,gymnasium orindoor swimmingpool

Corridor 45 60c) 45d) 45c) 55c)Music room 60 60 60 45 60Office or conference room 45 60 45d) 45 60

a) For corridor, office or conference room walls containing entrance doors, the STC rating of the basic wall, exclusiveof the door, should be 45. The entrance door should conform to the requirements of 4.5.5.

b) The STC rating for an ancillary space/toilet partition does not apply when the toilet is private and connected to aprivate office. An STC rating higher than 45 may be required for separating a quiet office or conference room froma common use or public use toilet or bathing room.

c) When the corridor will not be used as an ancillary learning space, the minimum STC rating may be reduced to notless than 45 or to not less than 40 for an exterior wall. Use of corridors as ancillary learning spaces should beavoided when they are located next to the noisy spaces indicated in the table by the high STC ratings.

d) When the need for acoustical privacy is critical, the STC rating should be increased to 50.e) See D2.3 in annex D for further guidance on the selection of appropriate STC ratings.f) NOTE d) of table 2 applies except that the STC rating may be as low as 40 providing the maximum A-weighted

steady background noise level in the adjacent ancillary learning space does not exceed 40 dB.

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technique is also recommended for partitions en-closing the ancillary learning spaces covered bytable 3. A method for estimating the STC rating ofcomposite partitions is provided in D2.4 in annexD.

4.5.5 Entry doors into classrooms and othercore learning spaces. To conform to the STC re-quirements of table 2 for composite walls, en-trance doors into classrooms or other core learn-ing spaces would be expected to have laboratorySTC ratings of 30 or more in their operable condi-tion. The STC rating for interior entry doors into, orbetween, music rooms shall be not less than 40.The location of classroom entry doors across acorridor should be staggered to minimize noisetransmission between these classrooms.

Provisions should be made to ensure that the pe-rimeter seals of sound rated doors are well main-tained. Seals for entrance doors should be in-spected and adjusted, as necessary, every sixmonths. The gaskets of door seals should neverbe painted.4.5.6 Impact Insulation Class IIC rating. Thefloor-ceiling assemblies of normally occupiedrooms located above core learning spaces shallhave IIC ratings of at least 45 and preferably 50. Ifa room below is an ancillary learning space, thefloor-ceiling assembly shall have an IIC rating of atleast 45. These IIC ratings shall apply without car-peting on the floor in the room above. In new con-struction, gymnasia, dance studios or other highfloor impact activity, shall not be located aboveclassrooms or other core learning spaces. For re-furbishment of existing structures, if it is not pos-sible to avoid such an incompatible condition, theIIC rating of the separating floor-ceiling assemblyshall be at least 70 when located above a corelearning space with an enclosed volume notgreater than 566 m3 (20 000 ft3); 65 when locatedabove a core learning space with an enclosed vol-ume greater than 566 m3 (20 000 ft3); and 65 whenlocated above an ancillary learning space. ClauseD2.5.1 in annex D provides further guidance onimpact noise isolation.

4.6 Conformance to acoustical performancecriteria and noise isolation designrequirements

It is recommended that conformance to the acous-tical performance criteria and noise isolation de-sign requirements be verified by test. However,this standard does not require testing to demon-

strate conformance. When optional tests are per-formed to verify conformance with the require-ments and recommendations of this standard, thefollowing procedures shall be followed.1) Tests to demonstrate conformance to the limitson background noise levels in table 1, 4.3.1, and4.3.2.1 shall be performed in accordance with theprocedures in E3 of annex E. If necessary, appro-priate tests shall be performed to demonstrateconformance with the limits on disturbing or timevarying noise from building services and utilitiesgiven in 4.3.2.2 and 4.3.2.3, (See E3.7.3 in annexE.)2) Conformance to the limits on reverberationtimes in table 1 shall be verified by calculation orby measurement procedures in conformance, orequivalent, to those in E4 of annex E.3) Conformance to the minimum sound transmis-sion class (STC) design requirements of table 2and the design recommendations of table 3 shallbe verified by field determination of the noise iso-lation class (NIC) as described in E5.1 in annex E.However, it shall be considered unnecessary toverify conformance to these noise isolation designrequirements and recommendations if conform-ance to the noise limits of table 1 is demonstratedfor the noisiest hour when learning takes place.4) Conformance to the impact insulation class (IIC)requirements of 4.5.6 shall be verified by the fieldtesting procedures in E5.2 in annex E.4.7 Conformance tolerances

When conformance testing or evaluation is per-formed, conformance to the requirements and rec-ommendations of this standard is demonstrated ifeach of the following is achieved. No additionaltolerances shall be allowed for the test methods orinstruments used for such demonstrations exceptas specified in this subclause.1) The measured A-weighted steady or unsteadybackground noise levels do not exceed the limitsspecified in table 1 and 4.3.1, respectively, bymore than 2 dB. The C-weighted steady back-ground noise levels do not exceed the limits in4.3.2.1 by more than 2 dB.2) Mean reverberation times, if calculated, do notexceed the limits in table 1 or, if measured, do notexceed the limits in table 1 by more than 0.1 s.3) All separating walls and floor-ceiling assemblieshave NIC ratings that are not less than a rating 5points below the required STC rating in table 2 or

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the recommended rating in table 3. For example,for a partition between a classroom and a speechclinic, conformance to the minimum STC rating of50 in table 2 is achieved if the NIC rating is not lessthan 45.

4) All floor-ceiling assemblies separating occupiedspaces from learning spaces below have a fieldimpact insulation class (FIIC) rating that is not lessthan a rating 5 points below the design require-ment specified in 4.5.6.

Annex A(Informative)

Rationale for acoustical performance criteria

A1 Introduction

The school classroom is an environment in whichspoken language communication facilitates andenables students to learn essential academic, so-cial, and cultural skills. Thus, the classroom servesas a communication channel for learning andshould be free of acoustical barriers. This informa-tive annex defines the perceptual, educational,and developmental rationale for the acoustical per-formance criteria specified in table 1 of this stan-dard. These rationales allow determination of thesignal-to-noise ratio and reverberation time thatcan ensure most children, adult learners, andteachers full and equal access to spoken commu-nication within the classroom. The acoustical per-formance criteria in the standard are derived fromempirical studies of classroom noise and rever-beration and their effects on speech communica-tion.

A1.1 Educational rationale

Intensive and continuous learning of social, intel-lectual, and communication skills occurs through-out childhood. A wide range of educational re-search studies [A1]* has shown that learning ispredicated on the ability to communicate with spo-ken language, and that language input and lan-guage proficiency form the bases for most cogni-tive skills. Additionally, other research [A2] hasshown that perception of spoken language pro-vides the foundation for the ability to read andwrite. Communication with spoken language is es-sential to most classroom learning activities. Typi-cally, as much as 60% of these activities involvestudents listening to and participating in spokencommunications with the teacher and other stu-dents. The central role of spoken language inclassroom learning underscores the need for aclear communication channel accessible to all stu-dents and teachers.

A1.2 Perceptual rationale

Communication with spoken language can occursuccessfully only when speech intelligibility is high.Research in speech perception [A3] has found thatwhen the background noise is very low, speechintelligibility depends in part on the absolute soundlevel of the speech, and in part on the absence ofexcessive reverberation.A1.3 Speech intelligibility in background noise

Most speech communication in classrooms occursin the presence of background noise. When back-ground noise is present, intelligibility depends onthe sound pressure level of the speech and alsoon the level of the speech relative to the level ofthe noise, that is, the signal-to-noise ratio (SNR)[A4]. The sound levels of both the speech andnoise are expressed as A-weighted sound levels indecibels. The relative speech to noise level, orSNR, expressed in decibels, is the sound level ofthe speech alone in the presence of backgroundnoise minus the sound level of the backgroundnoise.

Intelligibility increases as the SNR increases, ei-ther by raising the speech level or by decreasingthe noise level. Speech perception research [A5]has shown that individuals with hearing impair-ments, speech and language disorders, or limitedEnglish proficiency require more favorable signal-to-noise ratios than individuals without these im-pairments or disorders to achieve high levels ofspeech intelligibility.A1.4 Speech intelligibility in reverberantenvironments

Classrooms are enclosed spaces in which soundproduces reverberation. Reverberation times in

*[AX] designates reference [AX] in the bibliography at the endof this annex.

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excess of 0.4 s to 0.6 s reduce speech intelligibilityboth in quiet and in noise.When both background noise and excessive re-verberation are present, their effects on speechintelligibility are additive for individuals with normalspeech, language, and hearing abilities. Speechperception research [A4, A6] has shown that indi-viduals with impaired speech, language, and hear-ing abilities require signal-to-noise ratios that areat least 3 dB more favorable to offset their suscep-tibility to the negative effects of reverberation, ascompared with individuals without impairments.

A1.5 Selective acoustical barriers to learningproduced by background noise andreverberation

If spoken communication in the classroom be-comes inaudible or unintelligible for some studentsand teachers because of excessive backgroundnoise or reverberation, a clear communicationchannel is no longer accessible to these children,creating a selective acoustical barrier to learning.Neither the childs ability to understand in quiet northe adult teachers ability to understand in thenoisy classroom is a good predictor of when suchbarriers might exist. This difficulty in prediction isalso exacerbated by a young childs unawarenessof these barriers to learning.

A1.6 Scholastic achievement and theclassroom acoustical environment

The link between the acoustical barriers in theclassroom and the scholastic achievement of stu-dents has been evaluated in studies supportingthe objectives of this standard. The reading scoresof 2nd to 6th grade children in a school exposed tonoise from a nearby elevated urban train track [A7,A8] were compared in quieter and noisier class-rooms. The students, comparable in all respects,were receiving the same type of instruction. How-ever, the children in the lower grades and noisierclassrooms were three to four months behind inreading scores relative to those in the quieterclassrooms and as much as 11 months behind forthe higher grades. After a subsequent reduction ofthe track noise by 3 to 8 dB, the reading scores inthe noisy classrooms were still approximately oneyear behind those in the quiet classrooms.A major, controlled study of noise effects on scho-lastic achievement [A9] was carried out in 81

classrooms in 15 socio-economically matched LosAngeles schools located different distances fromfreeways. These differences caused the traffic-noise-generated indoor background noise to differby up to 19 dB between the noisiest and quietestclassrooms. Reading and math grade-equivalentscores evaluated for English-proficient students in3rd and 6th grade classes, showed a decrease ofapproximately 2.2 years between the noisiest andquietest schools for the 6th grade classes and 0.7years for the 3rd grade classes. This prominentnoise effect on grade differences in scholasticachievement is believed the result of either differ-ences in teaching style between grades or, moreinsidious, a possible cumulative, compounded ef-fect of poor acoustics on learning as a studentprogresses through school.A study of 13 schools in the United Kingdom [A10]compared their acoustical environment and corre-sponding speech communication conditions andteacher satisfaction before and after soundabsorbing treatment of the ceilings. After treat-ment, the average A-weighted background noiselevel in the unoccupied classrooms dropped from45 dB to 40 dB reflecting the decrease in reverber-ant background noise level. The average rever-beration time in the unoccupied rooms droppedfrom 0.7 to 0.4 seconds. The acoustically treatedclassrooms were favored by the teachers and pu-pils, who reported a greater ease of communica-tion and increased student performance.

A2 Developmental rationaleYoung children are more susceptible than adults tothe effects of background noise and reverberationon communication with spoken language. Be-cause of this susceptibility, young children also re-quire more favorable classroom signal-to-noise ra-tios and reverberation times to achieve the samelevel of speech intelligibility as adults do. Develop-mental status, linguistic and cognitive proficiency,temporary hearing impairments, and early recep-tive and expressive language disorders are all fac-tors that affect the greater susceptibility of youngchildren to background noise and reverberation.For example, in a longitudinal study [A11] of pre-school children in acoustically-treated or non-treated rooms in a child-care center, the children inthe treated rooms scored higher in number-letter-word recognition after one year of reduced noiseexposure than their cohorts in the non-treatedrooms.

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A2.1 Developmental status

Speech communication in unfavorable listeningconditions is a complex, high-level task requiring alevel of neurological maturity that is usuallyachieved only by 13 to 15 years of age. Conse-quently, young children may require more favor-able signal-to-noise ratios and shorter reverbera-tion times than older children require. Speechperception research [A12] has shown that 6-year-old children with normal hearing and normal lan-guage proficiency require signal-to-noise ratios 2dB more favorable than 15-year-old children toachieve the same level of speech intelligibility. The15-year olds, however, required the same signal-to-noise ratios as adults. In quiet listening condi-tions, the adults and both age groups of childrenhad good speech intelligibility.

A3 Hearing impairment

Young children are also more susceptible to tem-porary conductive hearing impairment caused byear infection (otitis media) than adults. Demo-graphic research [A13] has identified otitis mediaas the most common medical disorder in youngchildren, with an estimated incidence as high as25% to 30% among kindergarten and first gradechildren. Other research [A14] has found an inci-dence greater than 10% of mild high-frequencysensorineural hearing impairment among children6 to 19 years of age. Signal-to-noise ratio improve-ments of 3 dB to 5 dB together with increases inabsolute speech sound levels of 10 dB to 30 dBare necessary for children with these impairmentsto achieve the same level of speech intelligibility inclassrooms with high background noise.

A4 Language proficiency and languagedisorders

Children with expressive and receptive languagedisorders may also require more favorable signal-to-noise ratios to achieve good intelligibility, ascompared with children without these disorders.Research studies have shown, for example, thatchildren with language disorders have 10% to 40%poorer speech intelligibility in background noisethan children without these disorders, despitecomparable results in quiet environments. Chil-dren for whom English is not the first or primarylanguage may have limited English proficiency.These children are often learning English in schoolat the same time that they are learning the regularacademic curriculum.

Limitations in vocabulary and in the ability to fill inthe blanks when partial communication occurs indifficult listening situations have been shown to re-duce intelligibility for children with limited Englishproficiency [A15], again despite normal intelligibil-ity in quiet environments. These children may re-quire 2 to 5 dB more favorable signal-to-noise ra-tios in difficult listening situations to achieve thesame level of intelligibility as children with normalEnglish proficiency.

A related speech disorder problem caused by poorclassroom acoustics stems from the increased fre-quency of voice impairments and their conse-quences for communication. In noisy or reverber-ant classrooms, teachers are more likely to have toraise their voices. The results are higher inci-dences of voice impairment among teachers andchildren have greater difficulty hearing verbal in-struction presented by voice-impaired teachers insuch noise or reverberation.

A5 Determining appropriate acousticalperformance criteria and noise isolationdesign requirements

The acoustical performance criteria for this stan-dard are expressed in table 1 in terms of back-ground noise levels and reverberation times.Noise isolation design requirements for this stan-dard are given in table 2, in terms of sound trans-mission class (STC) ratings for enclosed learningspaces, despite the fact that the rationale for thesecriteria and requirements is based on absolute andrelative levels of speech. The terminology of thestandard is necessary because speech levels aredifficult to prescribe or standardize. However, theresearch literature on classroom speech soundlevels can be used to specify the expected rangeof speech sound levels seen throughout a class-room. These sound levels, together with knowl-edge of the signal-to-noise ratios and reverbera-tion times necessary for high intelligibility, wereused to determine the requirements for acceptablebackground noise levels and reverberation timesfor unoccupied, furnished classrooms in table 1.The background noise level criteria were, in turn,used to determine acceptable STC ratings forwalls, ceilings, and floors, in table 2, that will pre-vent noise from adjacent occupied enclosedspaces from exceeding the background noise levelcriteria in the classroom.

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A5.1 Classroom speech levels

Research studies [A16] of sound levels for conver-sational speech and teachers classroom speech[A17] show for the latter, the average A-weightedsound level is 67 dB at 1 m in a quiet classroom. Intypical classrooms with little reverberation, speechsound levels in the rear of the classroom may beas low as 50 dB. The criteria for background noiselevels in this standard assume minimum speechsound levels will be 50 dB anywhere in the class-room.

A5.2 Background noise levels

The 35 dB acoustical performance criteria forsteady classroom background noise levels in table1 were based on the assumption that a signal-to-noise ratio of at least 115 dB was necessary toensure that noise will not be a barrier to learningwithin a classroom. Assuming a minimum speechlevel of 50 dB, a signal-to-noise ratio of at least115 dB will always be achieved if the backgroundnoise level does not exceed 35 dB. The choice of115 dB for the signal-to-noise ratio was based onseveral considerations. The American Speech-Language-Hearing Association [A18] recommendsat least a 115 dB signal-to-noise ratio in class-rooms to ensure that children with hearing impair-ments and language disabilities are able toachieve high speech intelligibility.In addition, the research literature summarized inthis annex also supports a signal-to-noise ratio of115 dB.Normal adults typically require 0 dB signal-to-noise ratios for high speech intelligibility when lis-tening to simple and familiar speech material forshort periods of time. An additional 2 dB is neededto compensate for neurological immaturity; anadditional 5 dB is required to compensate forsensorineural and conductive hearing losses; anadditional 5 dB is required for limited English pro-ficiency and language disorders; and an additional3 dB is required to compensate for the effects ofexcessive reverberation. These additional require-ments for classrooms total 15 dB over that of nor-mal adults, or a signal-to-noise ratio of 115 dB.This conclusion does not include any further in-crease in the signal-to-noise ratio that may be as-sociated with the fact that children in the lowergrades may be listening to unfamiliar speech ma-terial.

A5.3 Reverberation times

According to available research data, the effects ofreverberation on speech intelligibility are con-trolled primarily by reverberation times at the threefrequencies specified in table 1:500, 1000, and2000 Hz. Based on this research, it was assumedthat reverberation times of 0.6 s, or less, in smalland mid-sized classrooms and 0.7 s, or less, inlarger classrooms will not degrade speech intelli-gibility excessively as long as signal-to-noiseratios of 115 dB or better are maintained. (Thereverberation times in table 1 are given for unoc-cupied, furnished spaces. For occupied spaces,the reverberation times are expected to be 0.1 s to0.2 s less than those in table 1.) These signal-to-noise ratios will be achieved if the backgroundnoise performance criteria also are satisfied. Thus,the acoustical performance criteria for both steadybackground noise levels and reverberation timesshould be satisfied simultaneously to ensure theelimination of acoustical barriers to classroomlearning.

A6 Bibliography on effects of noise andreverberation on learning

[A1] J.H. Flavell, Cognitive Development Prentice-Hall, Englewood Cliffs, NJ. (1977).[A2] G.W. Evans and L. Maxwell, Chronic noiseexposure and reading deficits: The mediating ef-fects of language acquisition, Environment andBehavior 29(5), 638-656 (1997).[A3] N.R. French and J.C. Steinberg, Factorsgoverning the intelligibility of speech, J. Acoust.Soc. Am. 19, 90-119 (1947).[A4] R. Plomp, A signal-to-noise ratio model forthe speech-reception threshold of the hearing im-paired, J. Speech and Hearing Research 29, 146-154 (1986).[A5] R. Plomp and A.M. Mimpen, Speech-recep-tion threshold for sentences as a function of ageand noise level, J. Acoust. Soc. Am. 66, 1333-1342 (1979).[A6] T. Finitzo-Hieber and T. Tillman, Roomacoustical effects on monosyllabic word discrimi-nation ability for normal and hearing impaired chil-dren, J. Speech and Hearing Res. 21, 440-448(1978).[A7] A. L. Bronzaft, A.I. and D.P. McCarthy, Theeffect of elevated train noise on reading ability,

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Environmental Behavior, 7, 517-528 (1975).[A8] A. L. Bronzaft, The effect of a noise abate-ment program on reading ability, J. Environmen-tal Psychology, 1, 215-222 (1982).[A9] J.S. Lukas, Noise, classroom behavior andthird and sixth grade reading achievement, Pro-ceedings, 17th International Congress of Acous-tics, Rome, Italy, (Sept. 2-7 2001).[A10] D.J. MacKenzie, D.J and S. Airey, Class-room acoustics, a research project, Heroit-WattUniv., Edinburgh, U.K. (1999).[A11] L. Maxwell and G. W. Evans, The effects ofnoise on pre-school childrens pre-reading skills,Journ, Environmental Psychology 20(1), 91-98(2000).[A12] D. Gelnett, L. Hinton and S.D. Soli, HearingIn noise test for children: Norming results andheadphone simulation, American Academy of Au-diology, Dallas, Texas (1995).[A13] S. Schappert, Office visits for otitis media:United States, 1975-1990, Vital and Health Sta-tistics 214, 1-15 (1992).

[A14] P. Ries, Prevalence and characteristics ofpersons with hearing trouble: United States, 1990-1991, Vital and Health Statistics Series 10 188,1-22 (1994).

[A15] C. Crandell and J.J. Smaldino, Speech per-ception in noise by children for whom English is asecond language, American Journal of Audiology5, 47-51 (1996).

[A16] C.V. Pavlovic, Derivation of primary param-eters and procedures for use in speech intelligibil-ity predictions, J. Acoust. Soc. Am. 82, 413-422(1987).

[A17] K. Pearsons, R.S. Bennett, and S. Fidell,Speech levels in various noise environments,Office of Health and Ecological Effects, U.S. Envi-ronmental Protection Agency. EPA-600/1-77-02(1976).

[A18] American Speech-Language-Hearing Asso-ciation, Guidelines for Acoustics in EducationalEnvironments, 37, Suppl. 14, 15-19 (1995).

Annex B(Informative)

Design guidelines for noise control for building services, utilities,and instructional equipment

B1 Introduction

HVAC systems and other building services andutilities are complex systems of mechanical, elec-trical, and plumbing components supplied by manydifferent manufacturers. This observation is par-ticularly true for most HVAC systems designed forspecific projects. Noise from these building sys-tems can be generated and transmitted to a roomin a wide variety of ways. Responsibility for provid-ing an adequate noise control design that will allowconformance to the background noise level limitsin table 1 resides with the architect and the archi-tects design subcontractors. During construction,responsibility for implementing the noise controldesign for each element of the building servicesmay rest with each individual subcontractor, butthe general contractor is likely to have overall re-

sponsibility to ensure that the design and imple-mentation conforms to the background noise levellimits in table 1.

B2 HVAC noise control

Specific limits on the maximum allowableA-weighted and C-weighted background noiselevel from HVAC equipment are given in 4.3. Toachieve these limits, an HVAC system should bedesigned with noise control in mind. The followingare some of the minimum features that should beemployed for HVAC systems intended for anylearning facility.

1) Unducted systems should not be employedsince the sound they produce is inherently unableto conform to the background noise level criteria intable 1.

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2) All grilles and diffusers (air devices) should beselected to have a catalog Noise Criteria (NC) rat-ing of NC 18 or less for a single diffuser, providingthe NC catalog ratings are based on a correctionof 10 dB for sound absorption in the room. [B1]

NOTE Noise Criteria (NC) is a single number ratingof room noise based on comparison of the octave-band sound pressure level spectrum of a noise withstandardized octave-band sound pressure level con-tours that include low-frequency sound (see annexG).

3) Airflow velocities in trunk ducts should not ex-ceed 4.1 m/s (800 ft/min). Branch ductwork sizesshould match the air devices duct connection size.Duct silencers will be required inside the air-han-dling unit or in the main supply and return air ductsin most systems.4) All ductwork should be fabricated and installedso as to achieve a low static pressure loss in ac-cordance with procedures in the Sheet Metal &Air-Conditioning Contractors National Association(SMACNA) for HVAC System Duct Design, [B2].To achieve the rated performance of air diffusers,the plenum depth should be the equivalent of atleast three to four diameters of the duct going tothe diffuser.5) All rotating equipment and equipment with staticpressure control dampers should be 3.3 m (10 ft),or farther if possible, from the classroom. HVACfan equipment serving more than one classroomshould be farther from the classrooms than equip-ment serving only one classroom.6) Centrifugal fans with airfoil-shaped bladesshould be used in most cases in order to achievethe background sound levels required for thelearning spaces. Centrifugal fans with forwardcurved blades should be avoided (especially withcentral air distribution systems) because this fandesign typically generates excessive low-fre-quency noise when the total static pressure isgreater than 2 inches of water.7) Ductwork serving adjacent learning spacesshould include sound attenuators or sound-ab-sorbing duct lining (if required), or both, to reducecrosstalk through the duct system. The attenuationshould be sufficient to preserve the noise isolationbetween the adjacent learning spaces.8) To minimize HVAC noise transmission into corelearning spaces, variable air volume (VAV) boxesand fan-powered boxes should not be located overthese spaces. Instead, the elements should be lo-

cated over less sensitive spaces, which may in-clude corridors.The above guidelines are examples of the manynoise control provisions that may be needed whendesigning an HVAC system. Before finalizing anyHVAC noise control design, considering the verylarge number of HVAC systems types that may beemployed for schools, the facility designer or theresponsible subcontractor should consult one ormore references such as those listed in clause B7.The ASHRAE Handbooks, [B3-B5] are especiallyhelpful to assist in achieving an HVAC system de-sign that will conform to the required minimumlevel of steady background noise. HVAC manufac-turers should be able to provide useful design ornoise-rating information for their systems or com-ponents [B6]. References [B7], [B8] and [B9] pro-vide further guidance on noise control for HVACsystems and other building services.

B3 Noise control considerations forelectrical equipment and systems

Significant background noise in a learning spacecan be produced by electrical equipment and itsinstallation. Two such sources of noise are electri-cal fixtures and light fixture ballasts. Light fixtureswith low-noise ballasts should be used in learningspaces to assist in conforming to the requirementsof table 1 for background noise levels. Improperinstallation of electrical or cable boxes can de-grade sound isolation between rooms. For singlestud walls, electrical outlet boxes on opposingwalls should never be in the same stud space. Fordual-stud walls, the boxes should be separated byat least 0.6 m (24 inches). If back-to-back electricalboxes are necessary in double stud walls, either ofthe following methods should be used. The boxesshould be enclosed in full gypsum board enclo-sures that do not contact the framing of the otherrow of studs and have all joints sealed with caulk-ing or both boxes should be of the vapor-barriertype that are properly caulked and sealed.

B4 Plumbing systems noise control

Water flow noise from plumbing systems can be asignificant contributor to the background noiselevel in a learning space. To minimize noise fromplumbing fixtures and piping located adjacent tocore and ancillary learning spaces, considerationshould be given to the following installation details.

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1) Run piping above corridor ceilings, not abovelearning spaces.2) Locate restrooms away from classrooms.3) Use cast iron waste water pipes, when possible.Plastic piping may require special care during in-stallation to ensure quiet operation and should bewrapped with one or more layers of sound-attenu-ating material or, for plastic waste pipe, wrappedwith sound-absorbing material and boxed in withgypsum wallboard.4) Isolate all water piping from the building wallsand structure using foam rubber wrapping or resil-ient clamps and hangers.5) When it is necessary for a plumbing wall chaseto be adjacent to a learning space, the wall shouldemploy double stud construction [with a minimum2.5 cm (1 inch) gap between the two rows of studs]with two layers of gypsum board on the classroomside and sound-absorbing insulation batts in bothstud cavities.

6) Reduce the pressure of the supply water asmuch as possible and employ trapped-air water-hammer arrestors for water supply pipes servingflush or solenoid valve fixtures to reduce waterhammer noise.

7) Use water siphon jet fixtures instead of blowoutfixtures.

8) Inspect all plumbing installations for conform-ance to the noise control features before sealingthe walls.

B5 Noise control for instructionalequipment used in a classroom

As stated in 1.1.4, the background noise from por-table or permanent, built-in equipment used duringthe course of instruction, such as audio-visualequipment or computers, is not within the scope ofthis standard. Cooling fans or other internal rotat-ing components usually generate this noise. Be-cause this noise can increase the backgroundnoise level in learning spaces, this equipmentshould be carefully selected and located to mini-mize its noise impact on the learning process. Ex-cept for computers, standards for the acousticalemission characteristics (for example, soundpower level) of such equipment are not currentlyavailable.

Such instructional equipment, when operating,should be located as far as possible from students

or placed in noise-isolating enclosures. This pro-cedure is especially important and practical forbuilt-in audio-visual systems or overhead projec-tors. For such built-in equipment, a design goalshould be to ensure that its operation will notcause the total one-hour average backgroundnoise level to exceed the limits specified in table 1while HVAC systems and other building servicesand utilities are also operating.The designer of the noise-control features shouldactively seek to determine whether potentiallynoisy instructional equipment is planned for per-mane

acoustical performance criteria

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