by Stephen Lind
Experts believe as many as one-third of all school students miss up to 33 percent of the oral communication that occurs in the classroom. Acoustics play an important role in creating a productive indoor environment and are especially critical in schools. Since much of K−12 learning hinges on hearing the teacher, sound control is a critical component of a high-performing school.
Research shows excessive background noise or reverberation in classrooms interferes with communication and listening and thus impedes learning. Additionally, poor school acoustics create extra challenges for students coping with learning disabilities, hindered by impaired hearing, or struggling to learn in a non-native language. (For more, see P. Nelson and S. Soli’s article, “Acoustical Barriers to Learning: Children at Risk in Every Classroom,” which was part of the October 2000 [vol. 31] edition of Language, Speech, and Hearing Services in Schools). Numerous articles in the Journal of the Acoustical Society of America (JASA) have highlighted studies showing students learn faster and comprehend and retain more knowledge in environments with the proper acoustics.(Examples from the periodical include “How Room Acoustics Impact Speech Comprehension by Listeners with Varying English Proficiency Levels” by Zhao Peng et al [vol. 134, 2013], and “Effects of Room Acoustics on Subjective Workload Assessment While Performing Dual Tasks” by Brenna N. Boyd, Zhao Peng, and Lily Wang [vol. 136, 2014]).
Due to these factors, design requirements for school acoustics differ from other commercial building spaces. The Acoustical Society of America (ASA) has created an American National Standards Institute (ANSI) classroom acoustical standard—discussed later in this article—to help ensure schools are designed correctly to create conditions conducive to learning.
HVAC equipment can play a key role in helping schools create quiet, comfortable classrooms for students and teachers. There are some considerations to keep in mind, but it is possible to meet classroom acoustic requirements with standard mechanical equipment and off-the-shelf components without adding significant costs in typical installations.
The importance of acoustics
Children can be ineffective listeners as they are still developing their speech perception abilities. This makes it difficult for them to separate speech from background noise or to correctly distinguish what is being said. Children need good acoustics to understand even familiar words and to learn new information. (P. Nelson’s article,“Sound in the Classroom: Why Children Need Quiet,” was in the February 2003 edition of ASHRAE Journal [vol. 45, no. 2]). These issues can be especially critical for students with learning disabilities or hearing impairments, as well as those dealing with common ear infections that can cause temporary hearing loss.
As children have different acoustical needs, neither engineers nor architects can rely on practices considered acoustically acceptable for adults when designing school spaces for teaching kids. There are both internal and external sound sources that impact noise levels in a school that need to be considered. External environmental factors can include nearby highways, airports, or rail lines.
Building mechanical systems, as well as school HVAC equipment with moving parts, can also contribute significantly to noise in a classroom. Fans, compressors, motors, and high-velocity fluid are the most common sources of distracting sound. Steady-state operation has been the focus of most standards and guidelines, but transient sounds due to starting and stopping can also result in disturbing or excessive noise. If acoustics are not considered when the building is designed, it is easy for mechanical equipment noise to become excessive in the classroom.