From the Baltimore Sun

Volume rises in debate on classroom acoustics

Wireless voice technology is catching on, but some experts sound a note of caution

By Liz F. Kay
Sun reporter

March 13, 2006    (Our letter sent to the Editor in response to this article appears below)

Surround sound does the job at the movie theater and in many family rooms and finished basements.

Why not in the classroom?

The Baltimore County school board has set aside $400,000 in its proposed budget to install and test "sound enhancement" systems - wireless microphones and speakers designed to distribute a teacher's voice evenly around the room. At least seven schools in the Baltimore area are already using it, and others in Maryland and across the country are investing in the equipment.

Proponents say the technology can help children hear lessons over the shuffle of papers and other classroom noises. They say it can also ease the strain on teachers' voices.

"It's the only way to be able to have the children in the back row hear the same as children in the front row," said Suzanne DeMallie, a Towson mother who lobbied the school board to consider the devices.

Generations have gone through school in classrooms without sound systems. And the State Department of Education and other agencies recommend trying to minimize background noise first, before installing the new technology.

But even as educators differ on the best way to improve classroom acoustics, most agree that the issue is an important one.

"Seventy percent of the time spent in a classroom is spent listening. That's how our educational systems are set up," said Pamela A. Mason, director of audiology professional practices at the American Speech-Language-Hearing Association.

She said the sound field amplification systems, as they are also known, were first developed for hearing-impaired children but that those with normal hearing benefit also.

Noises all around
A typical classroom is awash in sounds: the hum of overhead projectors, computers or ventilation systems; the kickball game outside; the roar of an airplane overhead. Hard surfaces such as tile flooring and painted walls reflect noise, as well as words, creating interference. It can be even worse in "open" classrooms without walls.

And children's hearing is not the same as adults'. Voices must be at least 15 decibels higher than the ambient noise for children to understand speech properly, said Paul J. McCarty, an adjunct professor of environmental psychology at Brigham Young University.

Adults require a much smaller difference because they can use context and other information to figure out what they've missed.

"Children haven't acquired enough life experiences to fill in the blanks, so to speak," McCarty said. It's especially important for children learning language to be able to hear similar-sounding consonants clearly.

On a recent morning at Sparks Elementary School, teachers and interns from Villa Julie College hooked the microphone headsets behind their ears or let them rest on their shoulders while they taught. One clipped a microphone to her collar.

A box mounted on the ceiling projected sounds to the rest of the classroom. Villa Julie intern Sara Saffell held the mike for third-grader Tanner Baldwin while he read a passage to the class. "You can move around the room and everyone can hear you," said her mentor, third-grade teacher Susan Schmelz.

Like the school in Sparks, schools in Anne Arundel and Harford counties have used some of their discretionary funds to buy amplification systems. The Prince George's County school system is testing the equipment in three elementary schools, a spokesman said. Districts in Florida, Ohio and other states are installing the systems in new buildings.

The State Department of Education and other agencies recognize that sound field amplification technology can help in existing buildings where attempts to improve acoustics have failed, according to a state classroom acoustics manual that will be published this year.

However, the guidelines do "not support widespread use of these systems in new construction." Instead, the manual states that the best approach is to design schools according to established acoustic standards.

Though the teachers' voices may be louder, the speech can be harder to comprehend in a classroom with lots of hard surfaces and a sound field system, Lou Sutherland, a fellow of the Acoustical Society of America, wrote in an e-mail.

Increased volume doesn't necessarily make announcements in train stations and arenas more intelligible, said Lois L. Thibault, coordinator of research at the U.S. Access Board, a federal agency that creates guidelines to reduce barriers for people with disabilities. Thibault said that introducing the system in a bad listening environment would create a "cocktail party" effect, where everyone is forced to speak louder.

Teachers and students could hear one another better if schools laid down carpet, installed sound-absorbing ceiling tiles or used other means to minimize noise from such sources as heating and ventilation systems, Thibault said. The practice of putting old tennis balls on chair feet helps reduce noise as well.

It may be expensive to fix acoustic problems in an older building, but good acoustic materials require no new batteries or maintenance, unlike the sound field equipment, Thibault said. "It's entirely possible to make rooms in which people can listen well," she said.

It can cost about $1,500 to $1,700 to outfit a classroom with a sound field system, McCarty and DeMallie said.

McCarty, a former elementary school principal, first heard about using microphones in classrooms about a decade ago, when one of his best teachers threatened to leave the profession because of voice strain. He said that when teachers used the equipment, standardized test scores improved at his school, even among students who were learning to speak English.

DeMallie, the advocate from Towson, said she first realized how a poor listening environment could impede learning when her son, now 7, was having trouble in kindergarten. He was diagnosed with auditory processing deficits, and after treatment he now enjoys school, she said.

She saw a television news segment last year about sound enhancement systems and was struck by how many children could be affected by poor acoustics.

The mother of three, who has worked as an accountant, researched the topic and has been a supporter ever since.

Teachers pleased
Teachers at Sparks Elementary, where the equipment was installed in all classrooms when it was built in 1998, say it has reduced the strain on their voices and has helped children focus.

Dogwood Elementary has six classrooms that use the systems, said a county school system spokesman.

Woodholme Elementary School Principal Maralee S. Clark said she used $13,000 from the school's equipment budget to install the systems in 10 kindergarten and first-grade classrooms and the media center.

Clark used it as a selling point when recruiting teachers for the Pikesville school, the county's newest.

"I didn't want my teachers not to have that advantage," Clark said.

Copyright © 2006, The Baltimore Sun

There were some misleading quotes and omission of some key facts about classroom acoustics in the above article that prompted ECH to respond with the following letter.

Dear Editor,

In reference to your 3/13 article entitled, "Volume rises in debate on classroom acoustics"  I would like to respond to some statements.  First, you cannot compare installation of a sound enhancement system (SES) in a classroom to increased volume in a sports arena or train station.  The purpose of a classroom SES is to help children (whose auditory capabilities are not as developed as adults) detect, discriminate and comprehend sounds for the purpose of learning.  This is the basis behind phonics and literacy which lead to higher level learning.  Most importantly, you MUST understand that a SES is only SLIGHTLY increasing the volume of the teacher's voice.  The main benefit is that the sound is equally distributed around the room, giving every child an equal opportunity to hear and learn.

The readers must understand that children with normal hearing need the teacher's voice to be 15 decibels louder than the noise in the room in order for that speech to be intelligible. (As mentioned in your article, this is 9 decibels louder than an adult would require.)  This is the most critical component of acoustics, and it is referred to as the SNR or Signal to Noise Ratio.  They must also understand that direct speech (the teacher's voice) drops 6 decibels for every doubling of distance.  So a teacher speaking at 65 decibels 3 feet in the front of the room will be heard at 53 decibels 12 feet from the front wall, and so on. (See diagram)  Yet noise, remains fairly constant around the room.  These two factors explain why children not seated close to the teacher miss out on information (up to one third of the information.)

The acousticians recommend making acoustical modifications to the classroom to cut down on reverberation and background noise.  The problem with this theory alone is that all the acoustical modifications possible will not correct the problem of the teacher's voice dropping over distance, and thus they ignore the required SNR of children. In fact, the ANSI standards that the MSDE recommends specifically exclude SNR from the scope of its standards. (See our FAQs page for details on this.)  This is because ONLY a SES with speakers evenly distributing the sound can ensure that ALL children in ALL areas of the classroom will hear the teacher's voice at the SNR of +15 decibels.  These same standards recommend a background level of noise in an UNOCCUPIED classroom, ignoring the reality of student occupied classroom noise.

It would be ideal to make all of the acoustical modifications AND install a sound enhancement system.  But, it would not be cost effective.  Acoustical modifications run well in excess of the $1700 cost of a SES, and ALONE cannot achieve the desired results.  I am not aware of any studies which show the benefits from making just acoustical modifications to buildings.  However, I have read the 50 plus studies that have been done showing improved academic performance, improved behavior, improved classroom management, improved literacy, reduced teacher absenteeism, high ROI, and reduced special education referrals from using Sound Enhancement Systems.  This research supports this small investment in our children's education.  A summary of these studies as well as many other important facts can be found at


Suzanne DeMallie
ECH Executive Director