Panasonic WX-LA20 Classroom Acoustics

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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