September 2015: School is in Session

Summer’s over. School’s open. From the School of Metropolitan Acoustics, this month’s newsletter is a mini-course on design features for good acoustics in classrooms.  So read on to audit Classroom Acoustics 101. Don’t worry; there is no quiz at the end!

Chapter 1:  SNR
Who hasn’t been on the phone in a noisy room and had to plug the other ear to hear?


What we’ve all been doing is increasing the signal-to-noise ratio (SNR). The signal, in this case, is the voice of the person on the other end of the line.  The noise is the sound from the talkers and activities around you. In classrooms – shuffling papers, shifting in seats, scraping of chair legs on the floor, footsteps, and talking all contribute to occupied noise. The HVAC system serving the classroom also contributes to the overall noise. For good retention of subject matter, research shows that the SNR should be +12 decibels (dB) or higher.  This means the voice of the teacher at the students’ ears should be 12 dB above the noise in the room, or roughly twice as loud as the classroom noise.

Chapter 2:  How Architectural Design Can Promote Learning
TypicalClassroomChapter 1 detailed how learning comprehension can be fostered by achieving a high SNR.  The architecture of the classroom plays a lead role in realizing this goal. The room dimensions, volume, shape, and surface finishes must work together to promote speech intelligibility and reduce the buildup of noise. The classic rectangular classroom design features reflective walls and floor and a mineral fiber lay-in ceiling tile; these do little to control occupied noise. Improving upon the classic, designers can specify a highly absorptive ceiling tile and add bands of absorption on the walls. Research conducted on the design of classrooms for speech intelligibility and learning (in particular from one of our staff members) has concluded that occupant noise will be reduced and SNR increased by using bands of absorptive panels at ear level around the room. Click here to read the article.

Chapter 3:  Engineered for SuccessClassroomHVAC
All too often, we see some noise-producing components of the mechanical systems in classrooms. Some classrooms have individual heat pump or fan coil units barely disguised by a metal cover panel. When these sources are present within the room, noise issues are common.  To create the best SNR possible, the HVAC system should be carefully designed to guard against excessive noise. Placement of units in closets or soffitted enclosures and lining ductwork and incorporating duct silencers are common ways to control HVAC noise.

Course Summary
Creating an environment suitable for learning requires coordination between all those involved in the design and construction of classrooms. A well-designed classroom considers every seat – equally offering all students the ability to learn. We hope this mini course refreshed the importance of designing classrooms with acoustics in mind.  As the saying goes, every day is a school day. Class dismissed.

Wyncote Elementary School – Wyncote, PA

October 2015: It’s All About The Base
August 2015: Riding the Information Autobahn