Children's Need for Favorable Acoustics in Schools

Peggy Nelson, Ph.D., CCC-A - nelso477@umn.edu
Department of Communication Disorders
University of Minnesota

Popular version of paper 1eID1
Presented Monday Evening, November 10, 2003
146th ASA Meeting, Austin, TX

Children perform more poorly than adults do on complex listening tasks such as trying to understand speech in noisy or reverberant rooms. This well-documented finding has clear implications for the design and construction of educational facilities. Recently the American National Standards Institute published standard S12.60-2002, "Acoustical Performance Criteria, Design Requirements and Guidelines for Schools" to address the issue. The tutorial session will focus on the research that forms the basis for the standard's recommendations.

Although children have good hearing soon after birth, show an immediate preference for their mother's voice, and discriminate characteristics of their native language within months of birth, there are some auditory abilities that continue to develop through adolescence. These include their ability to understand speech in noise, to separate speech from noise, and to ignore irrelevant reverberation. A body of behavioral and physiological evidence exists to demonstrate the maturation of these complex listening skills. The evidence will be presented in an overview at the tutorial session. This evidence includes some of the following points:

• Infants start as immature, broadband listeners (e.g., Werner & Boike 2001)
• Children don't put together the acoustic bits of information when they miss parts of the signal (e.g., Stelmachowicz et al., 2000; Eisenberg et al., 2000)
• Children don't weight important acoustic perceptual information of speech in the same way adults do (e.g. Nittrouer, 1996; Litovsky, 2003))
• Children are more distracted by noise than are adults, even when the noise is irrelevant or in the opposite ear (e.g., Wightman et al., 2003)
• Children don't segregate speech and noise as successfully as adults (e.g., Alain et al., 2003)

Because of these normal developmental effects, all children require greater signal-to-noise ratios (SNRs) and less reverberation than do adults. (That is, the target voice should be significantly louder than the background noise throughout the room, and the reflections off hard surfaces should be minimized.) Rooms that may seem appropriate for adult listening may be inappropriate for children.

Children who are especially adversely affected by noise and reverberation include:

1. children who are learning in a non-native language (possibly 25-50% of many urban classrooms)
2. children with hearing loss (approximately 10-15% of school children)
3. children with learning and attention deficits (approximately 10% of school children)

Children with those special needs comprise a significant proportion of all schools. Evidence from these listeners suggests that these children require SNR conditions such that the target voice is at least 15 dB louder than the background noise throughout the room. They also require rooms with minimal reverberation to control echoes.

Teachers, also, benefit from quiet classrooms. In recent studies of teacher vocal fatigue, 30% of teachers reported having voice problems, and reported noise as a primary environmental factor that adversely affected their teaching ability (Smith et al., 1998; GAO report, 1995). Classroom amplification systems can help, but cannot solve the problem of poor acoustics in schools.

Many U.S. schools do not provide the desired +15 dB difference between target signal and background noise, and contain hard walls and ceilings that produce unwanted reverberation. U.S. school construction projects currently underway are estimated at $20 billion. Schools that adhere to the standard's recommendation of maximum 35 dBA noise levels and 0.6 second reverberation times in classrooms will significantly improve the listening conditions for both typically developing children and for children with special needs.