Research on Vocal Disorders

Important Preface statement:

There are several ways to address auditory reception problems in the classroom. The three most commonly recommended ones are: 1) soundfield amplification, 2) vocal therapy for teachers and 3) acoustic treatment of individual classrooms. The long term risks and benefits of amplification in classrooms have not been fully explored. All teachers and administrators are strongly urged to get information from non-biased sources about the benefits (and potential risks) of amplification systems.

In the articles on this website, there are a number of statements about student performance improving as a result of the use of classroom amplification systems. These articles are lacking a description of WHY the children perform better. It has to do with how students perceive language. The ability to understand speech does not mature fully in children until about age 15. They do not have the experience with language that adults have. In effect, because adults have more experience, they are better able to fill in the blanks in the speech signal in a noisy environment. ASHA, the American Speech Language Hearing Association, has a great deal of information about this available. In their Position Statement and Guidelines for Acoustics in Educational Settings (ASHA 1995 (March): 37 (supplement 14): 15-19) they recommend that the volume of the teacher's voice be at least 15 dB above the background noise (signal to noise ratio of +15 dB). Children with normal hearing require a signal to noise ratio 2-3 dB higher than adults to achieve the same level of communication in conditions with background noise. There are many ways to achieve this ratio. One cost effective long term way is to construct teaching spaces so that ambient noise levels are kept low. Another is giving teachers voice training as a part of their teacher training. Amplification is only one of many options. It treats the symptom, but not the cause of the problem.

The Lombard Effect - how we speak louder in response to a loud environment - must also be considered. We raise the intensity of our voices by 3 db on average in response to every increase of 10 dB in background noise, starting at a threshold of 40 dB. So in response to background noise of 60 dB, we would on average increase our vocal output by 6 dB above that which we might use in a 40 dB level environment. Please remember that the dB scale is a log scale, so a 6 dB increase is a doubling of the intensity. One big reservation researchers and medical personnel have with across-the-board amplification of teachers in a classroom is that the classroom environment as a whole may get louder, not just the teacher. The teacher will be amplified, and in response students will talk louder; then, in order to be understood over the increased classroom noise, the teacher will raise the amplification level again, and the students will talk even louder. The damage in this case potentially spreads from the teacher's voice to include the students' voices and to everyone's ears.

The research on the use of amplification is by no means conclusive. All teachers and school administrators need to be aware that there may be potential dangers as well as benefits to teachers and students in classrooms that have amplification.

Here are some additional references for teachers:

  • Articles:

  • Article 1:

    "Vocal Strain Can Take Unseen Toll On Teachers" by Marc Pilotin.

    If Susan Dalton had continued putting off a visit to the doctor, she could have permanently lost something she needs in her classroom everyday: her voice.
    "Like any teacher, I was hesitant to take a day off work," says Susan Dalton, a seventh grade teacher at White House Middle School in White House, Tennessee.
    In the spring of 1995, Dalton suffered from what she thought was chronic laryngitis. Many days, her voice became hoarse. On other days, she could not speak at all.

    Dalton put off seeing a doctor. But after two months, when it finally became clear that the hoarseness was not going away, Dalton eventually visited Dr. Mark Courey of the Vanderbilt Voice Clinic in Nashville.

    Courey discovered nodules developing on Dalton's vocal chords. After a year of voice therapy produced no improvement, Dalton had surgery to have the vocal nodules removed. Without the surgery, Dalton could have permanently lost her voice.
    "I always had sore throats. I didn't think it was anything out of the ordinary," says Dalton.
    Many teachers may suffer from the same condition as Dalton--and, like her, incorrectly believe that it's something less serious.
    "Greater teacher awareness in the area of proper voice use is long overdue," says Courey, whose clients include country music artists. About 10 percent of his patients are teachers--a figure that belies the extent of the problem, Courey notes, since a high percentage of teachers complain about generic "voice problems."
    "The classroom setting is very demanding," says Courey. A combination of the classroom environment and the teacher's behavior can lead to vocal strain.
    To prevent damage to the vocal chords, Courey suggests paying attention to symptoms, which include neck pain and roughness in the voice.
    Teachers should never get to the point where they are hoarse at the end of each day, says Courey. "If the hoarseness persists for more than two weeks, it should get checked," he adds.

    Dalton, in her 12th year of teaching, now uses more non-verbal cues in class and has reorganized her lessons to provide for less time speaking. When she does speak to the class, she uses a microphone and transmitter clipped to her lapel, and her lectures are broadcast through a nearby speaker. And Dalton continues her rehabilitation.

    For more information, go to: http://www.nea.org/neatoday/0102/health.html

    Article 2

    "The Effect Sound Field Amplification has on Teacher Vocal Abuse Problems"
    by Laurie Allen, M.S., CCC-Aud.
    Keystone Area Education Agency
    1473 Central Ave.
    Dubuque, Iowa 52001

    During the 1994-1995 school year approximately 56% of 141 Dubuque, Iowa public elementary school teachers reported that they typically suffer from vocal abuse/fatigue problems at lease once each school year. Eighty-five or 60% of these teachers had never used sound field amplification equipment. These teachers estimated that they took 59 sick days each school year because of vocal maladies (7 sick days/teacher).

    Fifty-six or 40% of the teachers had experienced using sound field classroom amplification equipment. Those teachers estimated that when they were without the amplification equipment they averaged 52 sick days/year because of voice, jaw or throat problems (.93 sick days/teacher). But, when they had the use of the amplification equipment they estimated that they took only 19 sick days/year (.34 sick days/teacher). It should be noted that about half of the teachers reported that the sound field amplification equipment was user friendly and made it easier for them to project their voice throughout their classrooms.
    This data would suggest that an increased use of sound field amplification equipment would result in a substantial annual savings for the school district in substitute teacher pay. The Dubuque Community Schools currently employs approximately 650 full time teachers. Their substitute teacher pay is approximately $62.00 per day. Every 12-14 sick days saved by the District would cover the cost of another classroom amplification system.

    For more information, go to: http://www.customallhear.com/resources/voc144.htm