Understanding the ANSI standard for classroom acoustics.

IN 1998, groundbreaking studies from the United States Census Bureau and the American Medical Association concluded that learning among young school children is greatly impacted by noise and distraction. The additional test data that followed from studies conducted by parents, teachers and acoustical consultants around the country, revealed that classrooms were not being designed to mitigate these detractors.

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Background noise and reverberation have severe adverse effects on learning--especially in children between the ages of 6 and 13, who require a higher audible level in order to hear. Young children, because they are less efficient listeners than adults, require quiet conditions for optimal hearing and comprehension. Poor classroom acoustics create poor learning conditions, especially for children with speech impairments, learning disabilities, attention deficit and other behavioral disorders. And children facing language barriers, hearing loss and assistive hearing aids are even more disadvantaged.

According to the United States Census Bureau report published in 1998, nearly 20% of all school children are not native English speakers, and 5-11% are limited in their English proficiency. Another 1998 report by the Journal of the American Medical Association, reported that four out of 1,000 infants are diagnosed with hearing loss each year, and 13-15% have one-sided or mild hearing loss.

Combine these statistics with poor classroom acoustic design, and it is easy to see how studies and reports show school-aged children with normal hearing miss nearly 25% of classroom instruction, and children with hearing loss and language barriers miss almost 50%.

As a response to these alarming findings, the American National Standards Institute (ANSI) approved Standard S12.60-2002, a copy of which is available at no cost from asastore. aip.org. The standard sets forth the maximum background noise and reverberation time, as well as minimum sound isolation requirements between spaces and rooms.

For core classrooms with enclosed volumes less than 566 [m.sup.3], the maximum one-hour average A-weighted steady background noise level is 35 dB. The background noise criterion is based on a Signal to Noise Ratio (SNR--the sound intensity level produced by the signal source, in relation to the sound level of the background noise) of 15-decibels.

The maximum acceptable Reverberation Time (RT) is 0.6 seconds for classrooms with enclosed volumes less than 283 [m.sup.3] and 0.7 seconds for classrooms with enclosed volumes between 283 [m.sup.3] and 566 [m.sup.3]. (RT is the time it takes for steady sound in a room to diminish by 60 decibels after it has been turned off.)

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The sound isolation requirements (STC and IIC ratings) of materials and assemblies utilized between core learning spaces and adjacent spaces are also specified in the standard.

* STC 50 -- Between classrooms and open core learning spaces, speech clinics, health care rooms and the outdoors.

* STC 53 -- Between classrooms and public restrooms and bathing rooms.

* STC 45 -- Between classrooms and corridors, stairs, offices or conference rooms.

* STC 50 -- Between classrooms and private offices or conference rooms that require acoustical privacy.

* STC 60 -- Between classrooms and music rooms, mechanical rooms (with fans circulating airflow of 140 m3 or more), cafeterias, gyms and indoor pools.

* STC 60 -- Between classrooms and mechanical rooms with fans and vents with airflow less than 140m3, providing that background noise level in the classroom does not exceed 35dB.

Although it does not carry the force and effect of a building code, ANSI Standard S12.60-2002 is ASA's hope for eliminating poor acoustics in the educational environment. Its performance criteria and design requirements are easy to integrate into any project, and should be followed as much as possible-out of respect for its goal and mission.

Making the standard a part of your design begins with facility planning and carries throughout the entire construction timeline. Proper coordination among architects, general contractors, the facility design staff, equipment suppliers and manufacturers is the first step. Choosing building sites located away from major highways, airports and industrial plants comes next. Finally, designing a building layout that separates the noisy public zones from the quiet study areas completes the formula. To achieve the standard's guidelines, ANSI has outlined some recommendations as follows:

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Many acoustical doors and windows already meet Standard S12.60-2002 guidelines and offer the highest STC ratings in the industry today. They can be custom manufactured for any size you need as either single or double leafs, manual or power operated and with any finish you have in mind.

Because it utilizes design and construction techniques already familiar to architects and engineers, incorporating the ANSI Standard into your designs is easy and rarely requires the involvement of acoustical consultants. For those who view themselves as leaders in the industry, the Standard offers a great opportunity to raise the bar on quality construction for the educational industry. Those who choose to ignore it do so at the cost of their own good name and company image, especially if the standard does become a formal building code--a possibility that is not entirely unlikely.

About the Author: Darina Kotacka is the Assistant Marketing Director for Kreiger Specialty Products. She can be reached at darina@doorl2.com.

RELATED ARTICLE: STANDARD S12.60-2002 DESIGN AND SPECIFICATION IDEAS

* Specify wall and partitions that meet the minimum STC ratings set forth by standard.

* Specify ceiling tiles, floor materials and wall acoustic treatments with sound absorbing materials to meet the reverberation time requirements.

* Install wall-mounted lighting fixtures instead of ceiling fixtures to maximize the ceiling area available for sound absorption materials.

* Avoid fluorescent lighting because it emits a constant hum.

* Limit or eliminate open-space classrooms.

* Utilize sound control doors and windows to block interior and exterior noise.

* Staggered room entrances along corridors to reduce sound transmission through open doors.

* Place fans, compressors and other mechanicals systems away from classrooms

* Choose mechanical systems with low noise levels and operate them at low velocity.

* Avoid sharp edges and odd transitions within ductwork to lessen turbulence.

* Specify ductwork manufactured to achieve a low static pressure loss, and meets required airflow velocities, distances between inclusive components, such as air devices and volume dampers, and meets appropriate thicknesses and Noise Criteria (NC) ratings.

* Avoid window-mounted room air conditioners and ventilators as they do not conform to noise level criteria.

* Locate restrooms away from classrooms.

* Install plumbing piping above corridors instead of above learning spaces.

* Specify plumbing piping with appropriate sound absorbing materials and ideal sound reducing fixtures.

* Opt for furnishings and equipment, such as chairs and tables, compatible with the chosen flooring to eliminate additional noise.

* Choose instructional equipment with quiet monitors and fans and placed it in noise-isolated areas within the classroom.