HLAA Convention: From Mouth to Ear: Acoustic Architecture, Assistive Listening Devices and New Room Acoustical Standards - Part One

By Bonnie O'Leary

July 2010

Editor: One hearing loss topic that gets very little attention is ensuring that buildings and rooms meet appropriate acoustical standards. This is especially important for schools, because many children have difficulty hearing and/or understanding teachers in poorly designed classrooms.

Here's Bonnie's report on this important workshop at the HLAA Convention. This is part one of two parts.

~~~~~~~~~~~~~~~~~

This workshop was presented by Martha L. Jones, M.S., CCC-SLP, and Dan Schwartz. Martha presented her part of the program first. She is a speech-language pathologist who specializes in animal-assisted therapy at Central Park, Morning Star Elementary School in Bentonville, Arizona.

Martha's focus was acoustics in the classroom and its impact on learning, especially for children who have hearing loss. Poor classroom acoustics can cause reduced understanding of speech; deficits in reading and spelling ability; problems with behavior, discipline, and cooperation; poor attention; lower levels of concentration; reduced academic achievement; and interference with children's learning by affecting memory.

All children are affected by poor classroom acoustics. But the problem is more serious for children with bilateral or unilateral hearing loss, as well as children who have a temporary hearing loss (e.g., ear infection). It is a particular problem also for children who have learning disabilities, auditory processing disorders, and children who are not native English speakers.

What are good acoustics? According to the Acoustical Society of America, there is no single, all-encompassing set of criteria that will yield "good acoustics" for all rooms and uses. "Small classrooms, large lecture rooms, auditoriums, cafeterias, gyms, all have different acoustical requirements. To understand how these different spaces should be designed, we must first familiarize ourselves with a few basic properties of sound."

Direct sound travels from its source (person speaking) to the listener in a straight line without being reflected. It is easy for the listener to understand.

Background noise is any unwanted sound that interferes with what you are trying to listen to. Background noise in a classroom can include sounds from the outside, such as traffic, construction, children on the playground or it can come from other classrooms.

Reverberation is "the persistence of sound in a room once the sound signal has abruptly ceased," according to acousticalsurfaces.com.

Sound/surface interaction refers to what happens to the sound signal as it travels. Some goes through the surface, some is absorbed by the surface, some is reflected and some is diffused by the surface.

The longer a sound reverberates by bouncing off reflective surfaces, the higher the degree of distortion of speech sounds. In a classroom, it is important to have a short reverberation time, since the direct and early reflection energy makes it possible to understand speech in rooms.

What can be done to help reduce reverberation time? The following modifications are suggested by the Florida Department of Education:

1) Acoustic ceiling tile to absorb distorted middle and high frequency noise and improve speech perception ability
2) Soft surfaces on walls: fabric wall hangings, banners, student work, and hanging plants
3) Carpeting, particularly if it's installed over a pad, to help absorb excessive reverberation of high frequency consonant sounds and dampening noise from students and movement of classroom furniture
4) Draperies, blinds or shades to help buffer the reflective surfaces of windows; double-pane windows to help shield the classroom from additional outside noise
5) Cork boards help absorb sound; arranging classroom so instruction takes place away from noise surfaces such as HVAC units, and using carpet-covered study carrels to reduce noise from equipment or other students

In Ms. Jones' experience, her therapy dogs also act as a sound absorbing medium.

Central Park at Morning Star Elementary School, built in 2005, offers acoustic ceiling tile, window treatments, and cafeteria ceiling and wall tile.

Concluding her presentation, Ms. Jones discussed "The Lombard Effect", first documented in 1909 by Etienne Lombard, a French otolaryngologist. It refers to the involuntary tendency of speakers to increase the intensity, rate, and pitch of their voice when speaking in noisy environments. It causes reduced speech intelligibility as the overall noise level increases to overcome background and reverberated noise. Then the children and the teacher increase their vocal levels, including intensity, rate, and pitch. The noise level continues to rise, and Ms. Jones assured us it will drive you crazy!

Here's Part Two

~~~~~