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...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
1
direct sound energy.
Classroomaudio@us.panasonic.com
877.268.7215
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