Acoustics in Educational Settings
(Summary)
American Speech-Language-Hearing Association
ASHA, March 1995, 37, pp. 15-19
The American Speech-Language-Hearing Association (ASHA) maintains the
position that all students should be provided with appropriate acoustical
environments in educational settings. Without the proper acoustical
characteristics in these environments, students will see a decline in their
attention, behavior, speech perception and learning.
ASHA has suggested that schools try to achieve the following to improve
listening conditions:
• Minimize speaker-to-listener distances by ensuring students sit in the direct
sound field of the teacher. Because students cannot always be in close range of
the teacher, artificial methods such as assistive listening devices should be used.
• Place classrooms in low traffic areas and away from external noise sources
such as playgrounds and HVAC equipment.
• Locate classrooms away from large group areas such as gymnasiums,
cafeterias and auditoriums.
• Landscape (trees, shrubs, and earthen banks) to reduce noise from external
sources.
• Equip classrooms with heavy carpeting, thick curtains and acoustical wall and
ceiling panels.
Because many of the suggestions above are impractical in all classrooms, ASHA
strongly supports the use of assistive listening systems in classrooms.
Research indicates improved speech recognition in students, both with normal
hearing and with hearing loss, who use amplification systems. Extensive
research and studies of acoustical conditions in classrooms reveal excessive
noise (any auditory disturbance) and reverberation (reflected sound energy).
Continued….
…cont’d
ASHA provides three (3) guidelines for proper acoustic environments in
educational settings.
1. Unoccupied classroom noise levels should not exceed 30 dB(A) or a Noise
Criteria (NC) 20 dB curve.
• This guideline is recommended to help achieve the appropriate levels in
guideline #2.
• The most detrimental noise is generated inside the classroom (talking,
sliding chairs and desks) due to the similar frequency shared with that of
the teacher’s voice.
2. Signal-to-Noise Ratio (SNR) at the student’s ear should exceed a minimum of
+15 dB.
• Speech recognition tends to deteriorate at a deficiency of +15 dB for
students with hearing loss.
• Depending on grade level, studies have shown that SNR levels range
from +5 to -7 dB. Students with normal hearing require +6 dB SNR for
optimum communication.
3. Reverberation times should not exceed 0.4 seconds.
• Research shows reverberation in unoccupied classrooms ranges from
0.4 to 1.2 seconds. These delays lead to speech degradation by delaying
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direct sound energy.
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