Panasonic WX-LA20 Manual

Classroom Acoustics: A Failing Grade
(Summa ry)
Hearing Health, Sept/Oct 1998, pp. 11-16,59
Carl C. Crandell, Ph.D.
Recent investigations of the acoustical properties of classrooms and their impact
on students have revealed disturbing findings. Inappropriate acoustics can
negatively influence speech perception, on-task behavior, reading and spelling
ability, behavior, attention, concentration, and academic achievement. This is
extremely troubling for classrooms that house younger students as young
children require better acoustical environments than adults with normal hearing
to achieve equivalent perception scores.
A study conducted in the 80's demonstrated that noise was the sole factor for 50
– 75% of variant reading delays of elementary school children. When classroom
noise was reduced through acoustical modification, increases in concentration,
attention, and participation were seen. Acoustical improvements for classroom
environments include:
1. Acoustical modifications
The optimum levels for classroom acoustics are +15 dB signal to noise ratio
(SNR) and reverberation (reflected sound energy) times should not surpass 0.4
seconds. In 1995, a survey of 32 classrooms showed that only 7 met
recommended reverberation times and none achieved recommended noise
levels. An explanation for this lies in the fact that only a little more than half (59%)
of the rooms were carpeted, 15% had acoustical wall modifications, 3%
contained partitions or drapes, and none of the rooms had acoustically modified
furniture.
2. Reduction of speaker-to-listener distance (SLD)
This allows for the direct sound field to dominate the communication. When the
SLD is increased, the indirect sound field dominates the listening environment.
Speech recognition is only optimal within the direct sound field. To reduce poor
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