Other Assistive Listening Devices
This information is part of an online guide, Resources for Mainstream Programs
To address listening difficulties caused by distance or noise, assistive listening devices (ALDs) may be beneficial. ALDs enhance listening by directing a speaker's message directly to a student's ear. There are a variety of microphones and other devices available to enhance the auditory signal. Some of these devices are used in conjunction with a person's hearing aid, but others can be used independently. The purpose of these devices is to get sound to the ear as directly as possible without interference from distance, background noise, and reverberation. ALDs, similar to hearing aids, assist in making sounds louder and optimizing how sound is directed to the ear; they do not make sound clearer. Therefore, ALDs may have varying degrees of usefulness for persons with differing degrees of hearing loss. Before purchasing an ALD, it is wise to consult with an audiologist to ensure that the device is appropriate and that the student will benefit from it.
The type of ALD system most often used in schools is an FM system, although other systems, such as infrared systems, are available. FM systems function by using FM radio signals to send the teacher's voice via a transmitter/microphone to a student at a constant volume, regardless of the student's distance from the teacher. There are two kinds of FM systems: personal and sound-field.
- A personal FM system provides sound directly to an individual. Its design is similar to a hearing aid, or it may be adapted to an existing hearing aid. A personal FM system must be set for each student by the student's audiologist. If a student uses an FM system or other ALD, contact his or her audiologist or family to learn more about the system. The audiologist can show you how to use it and troubleshooting techniques for both the system itself and the use of it.
- A sound-field FM system provides increased and directed sound levels to a group of students. Special speakers are placed strategically throughout the classroom (even on a student's desk) to direct amplified sound where needed. As a result, all students sitting within range of the speaker benefit from the teacher's amplified voice.
One caution-the teacher's microphone of an FM system is very sensitive. It will pick up and transmit all sounds in close proximity to it, including noises made by jewelry or clothing rubbing against it. There are various types of FM microphones (i.e., boom microphone, lapel microphone) available that have various advantages and disadvantages. You can check with the student's family or audiologist to make sure the type of microphone in use is best for you and your classroom environment. Remember to turn the microphone off when it is not in use to avoid broadcasting conversations or bothersome background noises. For more information about FM systems, see http://www.asha.org/public/hearing/FM-Systems/ or http://www.boystownhospital.org/hearingservices/hearingBalance/Documents/FMSystems.pdf.
Infrared systems transmit sounds by invisible light beams. These systems cannot be used outside because of interference from sunlight. Infrared systems are perfect for TV listening and small group meetings. Relatively easy to set up, the transmitters connect directly to TV audio output jacks or can be used with a microphone. Receivers come in lavaliere or headset styles. For more information about infrared systems, see http://svconline.com/audioplayback/products/avinstall_ir_listening_systems/index.html or