Response to Petition for Rulemaking on Classroom Acoustics

ARCHITECTURAL AND TRANSPORTATION BARRIERS COMPLIANCE BOARD

36 CFR Chapter XI

[Docket No. 98-4]

Response to Petition for Rulemaking on Classroom Acoustics

AGENCY: Architectural and Transportation Barriers Compliance Board.

ACTION: Response to petition for rulemaking on classroom acoustics.

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SUMMARY: This document responds to a petition for rulemaking on

classroom

[[Page 60754]]

acoustics. The Architectural and Transportation Barriers Compliance

Board (the Access Board) will support the development of a standard on

classroom acoustical design by the American National Standards

Institute (ANSI) Committee on Noise (S-12), under the secretariat of

the Acoustical Society of America (ASA). Resources and technical

assistance on classroom acoustics are provided in this document.

FOR FURTHER INFORMATION CONTACT: Lois Thibault, Office of Technical and

Information Services, Architectural and Transportation Barriers

Compliance Board, 1331 F Street NW., suite 1000, Washington, DC 20004-

1111. Telephone number (202) 272-5434 extension 132 (voice); (202) 272-

5449 (TTY). These are not toll-free numbers. Electronic mail address:

[email protected].

SUPPLEMENTARY INFORMATION:

Availability of Copies and Electronic Access

Single copies of this publication may be obtained at no cost by

calling the Access Board's automated publications order line (202) 272-

5434, by pressing 2 on the telephone keypad, then 1, and requesting

publication C-12. Persons using a TTY should call (202) 272-5449.

Please record a name, address, telephone number and request publication

C-12. This document is available in alternate formats upon request.

Persons who want a copy in an alternate format should specify the type

of format (cassette tape, Braille, large print, or computer disk). This

document is also posted on the Board's Internet site at http://

www.access-board.gov/rules/acoustic2.htm.

Background

The Architectural and Transportation Barriers Compliance Board

1 (Access Board) is responsible for developing accessibility

guidelines under the Americans with Disabilities Act of 1990 (ADA) to

ensure that new construction and alterations of facilities covered by

the law are readily accessible to and usable by individuals with

disabilities. The Access Board initially issued the Americans with

Disabilities Act Accessibility Guidelines (ADAAG) in 1991. The

guidelines contain scoping provisions and technical specifications for

designing elements and spaces that typically comprise a building and

its site so that individuals with disabilities will have ready access

to and use of a facility. Although ADAAG contains a number of

provisions for access to communications, including requirements for

text telephones, assistive listening systems, and visible alarms, it

does not include provisions for the acoustical design or performance of

spaces within buildings and facilities.

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\1\ The Access Board is an independent Federal agency

established by section 502 of the Rehabilitation Act (29 U.S.C. 792)

whose primary mission is to promote accessibility for individuals

with disabilities. The Access Board consists of 25 members. Thirteen

are appointed by the President from among the public, a majority of

who are required to be individuals with disabilities. The other

twelve are heads of the following Federal agencies or their

designees whose positions are Executive Level IV or above: The

departments of Health and Human Services, Education, Transportation,

Housing and Urban Development, Labor, Interior, Defense, Justice,

Veterans Affairs, and Commerce; the General Services Administration;

and the United States Postal Service.

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On April 6, 1997, the Access Board received a petition for

rulemaking from a parent of a child with a hearing loss, requesting

that ADAAG be amended to include new provisions for acoustical

accessibility in schools for children who are hard of hearing. Several

acoustics professionals, parents of children with hearing impairments,

individuals who are hard of hearing, and a coalition of organizations

representing them had also urged the Board to consider research and

rulemaking on the acoustical performance of buildings and facilities,

in particular school classrooms and related student facilities.

On June 1, 1998, the Board published a Request for Information

(RFI) in the Federal Register to gather public input on this issue (63

FR 29679). The Board sought comment on a variety of issues in the

notice and indicated that it would determine a course of action after

evaluating responses to the notice. Alternatives included research,

rulemaking, and technical assistance on acoustical issues.

Approximately 100 comments were received in response to the RFI. The

preponderance of the comments were from parents of children with

hearing impairments and from professionals in acoustics and audiology.

Few comments were received from school systems.

A Board review of classroom acoustics also identified several key

issues. A third of the school systems cited in a 1995 General

Accounting Office study reported that acoustics for noise control was

their most serious environmental concern. Studies of elementary and

secondary school classrooms revealed that excessive background noise,

which competes with the speech of teachers, aides, classmates, and

audio educational media, is common even in new classrooms. School

construction is again on the increase and much public and governmental

attention is now being focused on education issues.

Comments

Commenters submitted research which showed how high levels of

background noise in classrooms compromise speech intelligibility for

children with hearing loss and other auditory disabilities and limit

the effectiveness of assistive technologies (such as hearing aids, FM

systems, and soundfield amplification) for such students, so that their

reading, communication, and learning skills may not develop adequately.

Audiologists noted that children, because they are neurologically

immature and lack the experience necessary to predict from context, are

inefficient listeners who require optimal conditions in order to hear

and understand. Those who miss key words, phrases, and concepts because

of poor listening conditions must struggle to keep up and may later do

poorly academically and suffer from behavior problems. At particular

risk are children who are experiencing temporary hearing loss from

otitis media (as much as 15% of the school age population, according to

a recent Centers for Disease Control analysis), children with mild to

moderate permanent hearing losses, children with speech impairments,

children who have learning disabilities and central auditory processing

disorders, children for whom English is a second language, and very

young children generally.

Acoustical consultants confirmed that controlling the reverberation

within a classroom and limiting the background noise generated both

outside and within a space could provide significant improvement in

speech transmission indices (STI) and signal-to-noise ratios (SNR)

necessary for optimal performance of assistive technologies. Heating,

ventilating, and air conditioning (HVAC) units and systems were

identified as primary contributors to classroom noise. It was also

noted that self-noise in classrooms can be dramatically reduced with

reductions in reverberation time and background noise.

Commenters familiar with school design and construction, including

State education agencies, architects, and engineers, agreed that

background noise and reverberation could be controlled using standard

means and materials of construction. It was noted that new computer

software makes it possible to quickly analyze listening conditions

under a variety of design, construction, and finishing and equipment

choices (basic acoustical design for classrooms

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can also be accomplished with pencil-and-paper calculations). Many

textbooks, manuals, and guides are available on architectural

acoustics, and include values for the noise resistance of wall

construction and the sound absorbency of common surfacing materials.

Recommendations for limits on reverberation and background noise in

classrooms have been included in architectural and engineering texts on

acoustics for more than 40 years.

Commenters pointed out that acoustical standards already exist in

the model building codes, particularly for housing; in several State

education and health department requirements for schools, in

requirements for Federal courtroom design and construction, and in the

building codes covering school construction in a number of European

countries. HVAC equipment is commonly rated for noise output under a

number of ANSI protocols, and the Los Angeles Unified School District

has recently begun to require manufacturers and installers to observe

noise thresholds on HVAC equipment placed in its schools. Two Fellows

of the Acoustical Society of America (ASA) noted that the Society had

formed a Working Group on Classroom Acoustics in 1997 under the ANSI

Committee on Noise (S-12) and recommended that the Board pursue the

joint development of a standard for classroom acoustics with the

Working Group, which was preparing a draft standard for consideration.

Action

Following a detailed analysis of the comments and research

submitted in response to the RFI, the Access Board agrees that many

classrooms are likely to include children for whom background noise

must be controlled in order to optimize listening conditions.

Furthermore, the Board has determined that collaboration with the

existing ANSI/ASA Working Group on Classroom Acoustics would be the

most effective way to develop technical and scoping recommendations for

classroom acoustics. On March 10, 1999 the Board voted to support the

efforts of the Working Group to draft a common standard for classroom

acoustics that will incorporate criteria for children with

disabilities. The ASA agreed to broaden the membership of the Working

Group to involve other groups, including representatives of school

systems, school designers, disability organizations, the U.S.

Department of Education, and the Access Board and committed to a 2-year

standards development process. The Access Board will fund some

administrative costs of the Working Group and will consider additional

funding, if necessary. After the standard has been ratified by the

Committee on Noise, the Board will pursue its enforceability under the

ADA or other statutes. This course of action is consistent with the

Board's goal to take a leadership role in the development of codes and

standards for accessibility and with the National Technology Transfer

and Advancement Act of 1995, which requires Federal agencies to

consider the use of private sector standards where appropriate.

In May 1999, the Working Group was expanded with the addition of

representatives of the Alexander Graham Bell Association for the Deaf

and Hard of Hearing (AG Bell), Self Help for Hard of Hearing People

(SHHH), the American Speech-Language-Hearing Association (ASHA), the

American Federation of Teachers (AFT), The American Institute of

Architects (AIA), the Council of Educational Facility Planners (CEFPI),

the Educational Audiology Association (EAA), the American Academy of

Audiology (AAA), the American Society of Heating, Refrigeration, and

Air Conditioning Engineers (ASHRAE), and the American Society of

Testing and Materials (ASTM). Other members may be added at the

discretion of the Working Group co-chairs, the Access Board, and the

U.S. Department of Education.

Both the Access Board and the U.S. Department of Education will be

active participants in the Working Group. In addition to the Acoustical

Society of America (ASA), Working Group members from the acoustical

professions represent the Institute of Noise Control Engineering (INCE)

and the National Council of Acoustical Consultants (NCAC).

The first meeting of the newly-expanded Working Group was held on

May 18, 1999 in Fairfax, VA to consider a draft standard. The next

meeting of the Working Group will take place on November 5-6, 1999 in

Columbus, OH. Other meetings will be scheduled as required. All

meetings will be open to the public. For further information, contact:

Charles E. Schmid, Executive Director, Acoustical Society of America,

365 Ericksen Avenue, Suite 324, Bainbridge Island, WA 98110, (206) 842-

6001, [email protected]. It is expected that a draft standard will be

recommended to the Committee on Noise in Spring 2001 for balloting.

Until a standard for classroom acoustics can be implemented, the

Access Board offers the following technical assistance for the

information of design professionals, schools, parents, and others who

seek guidance on how to provide an acoustical environment that supports

listening and learning.

Technical Assistance

Many factors, including design and construction methods, teaching

techniques, and amplification technologies, can affect the listening

conditions in a classroom. Primary among them is background noise, of

which there are several sources, some more amenable than others to

treatment by design and construction means. Self-generated noise, for

example, particularly in the lower grades, may be difficult to control.

While a quiet room can minimize the need for raising the voice (and

carpeting can soften the sound of footfalls and furniture), self-noise

can be only partially ameliorated by architectural means.

Reverberation--sounds that reflect from hard surfaces and arrive back

at the listener's ear at different times--adds to background noise

levels and smears the clarity of direct sound, thus reducing speech

intelligibility. Fortunately, reverberation is relatively easy and

economical to control--even in existing classrooms--by adding absorbent

materials to certain room surfaces.

Speech Intelligibility

Background noise both competes with and obscures the useful speech

and other signals in a classroom. The greater the noise and

reverberation in a room, the louder the signal must be to be heard and

understood. Speech intelligibility is in part a function of the signal-

to-noise ratio (SNR). The SNR at a child's ear is the difference

between the loudness of the signal (the teacher's voice, for example,

typically about 60 dB) and the loudness of the competing noise in the

room, from heating, ventilating, or air conditioning systems or other

noise from within or outside the classroom (often measured in the 45-55

dB range in classrooms). And because loudness varies with distance

(every doubling of the distance between speaker and listener causes a 6

dB drop in signal loudness), the SNR will vary as a child or teacher

moves about the classroom.

Decibel levels are usually measured at 3 feet from the speaker.

When there are 6 feet--twice the distance--between speaker and

listener, only 54 dB of the 60 dB delivered by the typical teacher

reaches the student. At 12 feet, only 48 dB arrive. At 24 feet--the

back row of a small classroom--only 42 dB will be audible. In some

locations and at some times, the loudness of the background noise in a

classroom may well exceed

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the loudness of the desired sound signal. Research has shown that

children who have temporary and permanent hearing loss need an SNR of

at least +15--that is, 15 dB greater than the background noise--for

adequate speech intelligibility.

Children with other disabilities will also benefit from good

classroom acoustics. In particular, children who receive speech

therapy--the most frequently delivered special service in elementary

schools `` need good listening conditions for themselves and their

listeners. Research suggests that children who have auditory

processing, language, and learning disabilities, particularly attention

deficit disorders, find it easier to focus on an educational task if

the SNR is higher. Audiologists have also called attention to children

at risk because of age (young children just acquiring language

generally need higher SNR values than adults) and native language

(children for whom English is a second language have similar needs).

Every student will learn more effectively in good listening conditions,

but for children with hearing loss, including the often-undiagnosed

temporary losses due to the common, chronic ear infections of

childhood, good acoustics are an essential basis for learning and for

other remediations necessary to learning.

Amplification

Many children with hearing loss will use both personal (hearing

aid) and classroom (radio frequency or FM) amplification to maximize

SNR values. Amplification technologies can supplement the speech signal

but cannot compensate for (or overcome) a poor acoustical environment.

To be effective, amplification requires control of reverberation times

and background noise. Furthermore, background noise, when amplified,

can be painful and disruptive for children with a variety of auditory

disabilities.

Many schools are now installing soundfield systems--amplification

distributed throughout the classroom--to improve listening conditions

for all students, not just those who have hearing impairments. Note,

however, that such amplification will add to background noise in work

areas within the room and may impinge on adjacent spaces without

adequate acoustical barriers in partition walls. In addition, most

assistive listening and soundfield systems require that the speaker use

a microphone, which may not always be feasible in group situations.

Input from other speakers--aides, peers, and audio equipment, for

instance--will not generally be amplified, and casual remarks may be

missed. Educators recognize that the incidental learning that occurs in

a classroom is as important to socialization, skill mastery, and self-

esteem as is the formal curriculum delivered by the teacher. And

instructional methods are changing to small-group, computer-supported

learning that makes it difficult to utilize these amplification

technologies. By optimizing basic room acoustics, design professionals

can ensure that all children have maximal access to teaching `signals',

both directly and through assistive technologies.

Design Issues

The characteristics of good architectural acoustics and the means

to achieve good listening conditions in classrooms are well-known and

not difficult or costly to apply in new construction and alterations.

School architects who have had a standard education in HVAC and

acoustical design may not even require the services of the acoustical

consultant they would expect to include in a contract for the design of

an audiovisual facility, auditorium, or concert hall. Facility and room

acoustical design for good listening and learning environments will

consider:

Site, space, and classroom adjacencies that minimize

classroom exposure to environmental, equipment, and occupancy noise;

Room size and proportion for appropriate sound reflection

and absorption;

Slab, ceiling, roof, and wall construction (including

doors and windows) that are appropriate barriers to noise;

HVAC equipment selection, system design, and installation

that minimizes structure, duct, and operating noise;

Finishes selected and located for proper reverberation

control, and

Attention to electronic and radio-frequency interference

with assistive devices.

Good detailing, tight specifications, and careful construction and

finishing will also be necessary to ensure that the facility and the

spaces within it meet design intent. In general, the objectives of

classroom acoustical design should be to control and limit background

noise and reverberation.

Background Noise

Noise can be mitigated at the source, along its path, and at the

receiver. A combination of small improvements at each point can often

produce the most cost-effective noise reduction. In general, favorable

architectural acoustics will depend upon construction that resists the

passage of sound, finishes that absorb sound energy, and HVAC design

that minimizes noise output.

The now-common practice of heating, cooling, and ventilating

classrooms using through-the-wall or roof-mounted units has had a

significant and deleterious effect on classroom acoustics. Few

manufacturers have yet been motivated to control the noise of fans,

compressors, and air movement through grilles that contributes the

largest proportion of background noise in most existing classrooms. The

research literature is replete with teacher reports of the need to turn

off the heating or cooling unit during important lessons. Children with

hearing loss must always be seated away from such noise sources and

close to the teacher. While retrofit enclosures can achieve a reduction

in noise output, it has been found to be a costly fix that few schools

will fund. Ducted (and piped) systems with central HVAC equipment are

much more suited to noise management through isolation and the

manipulation of duct sizing, length, openings, and lining, but are

often a casualty of cost-cutting. Unit ventilators are typically

specified for hotel and motel guestroom construction where the

background noise they contribute helps maintain acoustic privacy

between rooms; as currently engineered, they are not appropriate for

spaces in which communication is a primary function. What is most

needed is a collaboration between schools, designers, and manufacturers

to reduce the noise levels of such units, a re-engineering process that

is being applied to many appliances and equipment.

Background noise from the exterior environment can be managed with

wall construction of appropriate sound resistance and the specification

of multi-pane glazing and well-insulated and isolated frames typically

required for energy conservation (sound reduction can be enhanced by

pairing glass of different thicknesses). Windows and other openings are

the weak link in building enclosure. Where exterior noise is

significant, it will not be possible to maintain speech intelligibility

in classrooms with the windows open.

Background noise can also enter the classroom from adjacent

spaces--other classrooms, the gymnasium, cafeteria, or auditorium, and

corridors--through walls, doors, plumbing chases, and ducts. Sound-

resistant slab, wall, and ceiling construction and well-gasketed,

sound-rated doors are the answer here. When designing building alarm

systems,

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it is a good idea to pair visible (strobe) and audible alarms in

classrooms, since room enclosures with high Sound Transmission Class

(STC) values may mute corridor bells.

Noise generated within the classroom also contributes to background

noise levels. Audio-visual equipment, computers, the pump in an

aquarium, even lighting ballasts add decibels to the mix. The self-

noise of students working in small groups can be mitigated by

increasing absorbent surfaces. Carpeting is used in many elementary

schools to quiet the noise of footfalls and furniture shifting by

younger children, who need higher SNRs for speech intelligibility.

Recent advances in carpet technology have led to the availability of

bacteria-resistant floor coverings.

Reverberation

Reverberation is the measure of the time (in seconds) that it takes

a given sound to decay by 60 decibels. Long reverberation times are not

desirable because late-arriving sounds blur speech clarity and increase

background noise. However, early sound reflections in rooms can

actually reinforce the speech signal and improve SNR if they arrive at

the listener's ear within 50 milliseconds. By placing materials to

reflect early sound and absorb late-arriving noise, it is possible to

optimize the reverberant characteristics of a given room.

A recent paper by Rebecca Reich and John Bradley of the Canadian

National Research Council reports on their investigation of classroom

reverberation through computer modeling. Using the ODEON room acoustics

ray tracing program (version 2.6 for DOS), researchers were able to

identify optimum conditions for speech as a reverberation time of 0.5

seconds (the research also showed that speech intelligibility varied

only one-half of one percent between reverberations of 0.3 and 0.6

seconds). Nine different placements of material, each with the same

total of sound absorption, were tested. When the source position was

located at the head of the room, in traditional classroom style, speech

clarity was found to be optimal when the absorptive material was

located on the upper portions of classroom side and rear walls.

Interference

Interference from lighting ballasts, radio frequency sources, HVAC

controls, and other electrical, electronic, microwave and even infrared

sources can compromise the effectiveness of assistive technologies and

has become an increasing problem for many people who are hard of

hearing. Young children with hearing loss may not be able to identify

and call attention to malfunctioning devices. In extreme cases, such as

schools located in the path of transmission towers or equipment, it may

be necessary to install shielding in exterior wall and roof assemblies.

Accessibility Recommendations

In 1995, the American Speech-Language-Hearing Association (ASHA)

published a Position Statement on Acoustics in Educational Settings

that called for ``appropriate acoustical environments in all

educational settings, to include classrooms, assembly areas, and

communications-related treatment rooms''. ASHA's Acoustical Guidelines

recommend that:

Unoccupied classroom noise levels should not exceed 30

dB(A) or a Noise Criteria (NC)-20 curve 2

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\2\ NC curves weight sound pressure levels across 8 standard

frequencies to approximate human perception of sound, which is

greater in the high frequencies. To meet NC-20, sound pressure level

at the lowest standard frequency (63 Hz) can be as much as 50 dB,

while at the highest frequency (8000 Hz) it can be no more than 16

dB).

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Reverberation times should not exceed 0.4 seconds, and

The SNR at a student's ear should exceed a minimum of +15.

The ASHA recommendations are backed by substantial research and are

the most authoritative on the subject of listening conditions for

children who have hearing loss and other disabilities. An extensive

bibliography is included. Self Help for Hard of Hearing People (SHHH),

an advocacy organization, has endorsed the ASHA guidelines. AG Bell, an

organization whose membership is over 50 percent parents of children

with hearing loss and includes many professionals who work with

children, advises its members to utilize the ASHA guidelines in

advocating for an appropriate acoustical environment for children with

hearing loss.

Industry Recommendations and Standards

Industry coverage of acoustical issues rarely includes discussion

of the characteristics of good listening conditions for people who are

hard of hearing, although specialists in the design of facilities for

people who are elderly have begun to recognize this as a significant

issue. Acoustical design for children's environments is not typically

distinguished from practices suitable for adults.

Criteria for classroom listening conditions at three levels of

quality were recently outlined in ``Goals and Criteria for Acoustical

Planning'', a presentation by R. Kring Herbert, FASA, at the 1999

conference ``Eliminating Acoustical Barriers to Learning in

Classrooms'' in New York City, organized by the coalition formed to

submit comment to the Board's RFI:

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A-weighted

Listening conditions sound level Room criteria (RC), Neutral 1 RT-60

(dBA) (seconds)

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Desirable (new construction)......... 31 RC-25N 0.5

Adequate (alterations)............... 36 RC-30N 0.5

Poor................................. 41 RC-35N 0.5

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1 Room criteria ratings were developed to assess the effect on listeners of HVAC noise, which can be annoyingly

``hissy'' (H) in the high frequencies and ``rumbly'' (R) in the low frequencies. Sound pressure levels for RC

curves are lower at both extremes (46 dB maximum at 63 Hz and 13 dB maximum at 8000 Hz for RC-20) than NC

curves, although they are identical at mid-range (26 dB at 500 Hz).

Textbooks on acoustical design typically contain guidelines for

maximum background noise in different occupancies. Recommendations in

current publications show a range of 25 dB(A) to 35 dB(A) maximum for

the interior sound level in unoccupied classrooms. Most texts do not

distinguish between classrooms for children and classrooms for adults.

Only Egan, of those consulted in the Board's analysis, considered hard-

of-hearing users. Egan recommends a 5 dB reduction in background noise

for facilities serving people who have hearing loss. Reverberation

times between 0.5 and 0.8 seconds have been recommended for classroom

uses.

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The American Society of Heating, Refrigeration, and Air

Conditioning Engineers (ASHRAE) in its 1995 Handbook suggests a Room

Criteria maximum of RC-40N for small classrooms ([email protected] and contains links to other sites of

interest. Professional members include the Acoustical Society of

America, Alexander Graham Bell Association for the Deaf and Hard of

Hearing (AG Bell), the American Academy of Audiology (AAA), the

American Speech-Language-Hearing Association (ASHA), the Educational

Audiology Association (EAA), the National Council of Acoustical

Consultants (NCAC), Self Help for Hard of Hearing People (SHHH), and

the Council of Educational Facility Planners, International (CEFPI).

The U.S. Department of Education maintains a National Clearinghouse on

Education Facilities. Its website on classroom facility design at

http://edfacilities.org includes references to research and

publications on classroom acoustics.

Additional reading and reference material, including electronic

links to other websites of interest, will be posted on the Access

Board's website at http://www.access-board.gov/rules/acoustic3.htm.

June I. Kailes,

Chair, Architectural and Transportation Barriers Compliance Board.

[FR Doc. 99-28941 Filed 11-5-99; 8:45 am]

BILLING CODE 8150-01-P