June 2007 — Features
Print this article | Email this articleClick here to receive your FREE subscription to T.H.E. Journal
Sound Solutions
Poor classroom acoustics are impairing students’ hearing and their ability to learn. The need for audio amplification systems is coming through loud and clear.
"The square of the high moose he calls some of the squares of the other two sides.” Some students will tell you that’s the Pythagorean theorem. No, they’re not dumb; no, they don’t have attention deficit disorder; and no, their teacher doesn’t enunciate poorly. In many instances, even if they sit just six feet away from the speaker, they simply can’t hear.
The problem isn’t one of volume. In fact, what usually happens in a classroom when students say they can’t hear is that the teacher speaks louder. That may be fine for vowels, but it doesn’t do much for consonants— and it’s generally the consonants that provide the intelligibility: An oo ee i ats o? (Can you see why that’s so?) And even a loud voice isn’t likely to make it to the students in the back row if the classroom has bad acoustics. The only tangible result is usually teacher vocal strain.
Rather, student hearing difficulties are largely the result of three factors:
- A child’s auditory neurological network isn’t fully developed until around age 15. For purposes of comprehension, children require louder voices and a quieter ambience than adults do.
- Classrooms are noisy. There’s noise from other students, from computers and printers and lights and heating systems, and from people in the hallways and traffic outside.
- Students don’t have the experience to “guess” at what they hear. If they don’t know the word hypotenuse, then they can’t process hearing “high moose” as anything but “high moose”—they can’t make the connection. And this is exacerbated if the student isn’t a native English speaker or really does have a hearing deficit.
The main problem, as Debbie Tschirgi, director of educational technology programs for Educational Service District 112 in Vancouver, WA, explains in her widely referenced white paper, “Classroom Amplification Systems: Understanding and Overcoming the Acoustical Barriers to Learning,” is inadequate signal-to-noise ratio in US classrooms, which impedes communication. She says that while the American Speech-Language-Hearing Association recommends a classroom noise level no higher than 30 decibels, the typical classroom has noise levels that range from 41 to 51 dB. (Keep in mind that loudness is measured on a logarithmic scale: A 40-dB classroom is 10 times as loud as a 30- dB classroom.) Tschirgi’s research indicates that for teachers to communicate well, their voices—or signals—should be 15 decibels more than that of the background noise, a “score” of plus 15. But she finds that most classrooms have signal-to-noise ratios ranging from minus 7 to plus 4.
