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Classroom Acoustics: A Failing Grade

(Summary)

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

Continued…

…cont’d

classroom acoustics, close SLD should be utilized whenever possible. One way

to improve SLD is to use small group instruction over traditional seating

arrangements.

3. Utilization of classroom amplification

The implementation of classroom amplification can decrease SLD and

significantly affect speech perception. The Mainstream Amplification Resource

Room Study (MARRS, 1981) demonstrated drastic improvements in academic

achievement when students received amplified instruction.

By increasing the teacher’s voice by approximately 10 dB and providing a

uniform sound field throughout the classroom, students display perceptual and

psycho-educational improvements.

The large body of acoustic research in classrooms supports the need for good

acoustics in teaching environments. Several strategies can alleviate the

damaging effects of poor acoustics, one of which includes sound field

amplification. By adopting these solutions and strategies, it will be in the best

interest of the students.

Classroomaudi[email protected]

877.268.7215