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Know-How: Acoustics

Acoustics standards for background noise and reverberation in classrooms may be adopted soon as part of the International Building Code (IBC).

The U.S. Access Board, which is responsible for developing and maintaining accessibility standards as set forth in the Americans with Disabilities Act, worked with the Acoustical Society of America on the guidelines.

“If followed, this standard removes acoustical barriers to learning,” says Paul Schomer, standards director for the acoustical society. “It provides equal access to education for a sizable minority of school children in the United States who may have mild to moderate hearing, learning or attention deficits, suffer frequent ear infections, have limited English language skills, or may otherwise suffer from a substandard acoustical environment. For teachers, working in a classroom that conforms to this standard can reduce or eliminate voice strain and reduce stress.”

Lois Thibault, coordinator of research for the Access Board, says the recommendations call for unoccupied classrooms to have a maximum background noise of 35 decibels and reverberation time of 0.6 to 0.7 seconds.

“We think that they are going to adopt the recommendations,” says Thibault. “The issue needs attending to.”

The standard would be voluntary unless it is incorporated into a code, ordinance or regulation, the Access Board says. If the proposals are incorporated into the IBC, the classroom acoustical requirements will become part of the building codes in those jurisdictions that use the IBC or its member codes.

If the standards are not accepted, the Access Board is likely to develop acoustics standards on its own that would become part of its ADA Accessibility Guidelines, says Thibault.

The board says that high levels of background noise in schools, much of it from heating and cooling systems, adversely affect learning environments, particularly for children with hearing loss and young children.

One group that has opposed adoption of the proposed standards is the Air-Conditioning and Refrigeration Institute, which contended that the recommendations were too stringent and would force that industry to develop new and costlier equipment.

The Access Board became involved in the issue after the parent of a student with a hearing disability requested changes in the accessibility guidelines to address acoustical standards for classrooms.


0.6 to 0.7

Recommended standard for reverberation time, in seconds, for an unoccupied classroom.
Source: Access Board


Minimum signal-to-noise ratio, in decibels, that is necessary for good speech intelligibility in a classroom.
Source: Acoustical Society of America


Recommended maximum, in decibels, for background noise in an unoccupied classroom.
Source: Access Board


Percentage of the school-age population that may suffer from temporary hearing loss.
Source: Centers for Disease Control


Recommended minimum Noise Reduction Coefficient (NRC) for classroom ceiling tiles.
Source: Acoustical Society of America

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