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Acoustical Society of America
ANSI S12.60-2002 American National Standard Acoustical
Performance Criteria, Design Requirements, and Guidelines for
Schools
is made available to the end user as a public service by the
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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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The American National Standards Institute, Inc. (ANSI) is the
na-tional coordinator of voluntary standards development and the
clear-inghouse in the U.S. for information on national and
internationalstandards.
The Acoustical Society of America (ASA) is an organization of
sci-entists and engineers formed in 1929 to increase and diffuse
theknowledge of acoustics and to promote its practical
applications.
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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
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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.
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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
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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
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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
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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
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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
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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
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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