Simple Assistive Technology, continued

Assistive Listening Devices (ALD). These are hearing assistance products designed to help people in settings where background noise, distance from the sound source, or poor acoustics make hearing especially difficult. ALD's differ from hearing aids in that they are intended for situational use rather than continuous use and they are not custom-fit to the individual. ALD's can be used as stand-alone systems, or in combination with personal hearing aids.

The primary function of an ALD is to maximize the desired sounds (signal) while minimizing undesired sounds (noise). This is called improving the signal to noise ratio. ALD's accomplish this by placing a microphone as close as possible to the desired sound source (typically a person speaking). The microphone signal is then carried via a cord or by wireless signal to an amplifier which drives an earphone, headphone, or hearing aid coupler. There is a volume control on the amplifier and some have tone controls as well.

Sound/Field FM Systems. These provide amplified speech from a microphone worn by a speaker to a loud speaker directed at an entire room or parts of a room (in contrast to reception by the individual headphones used in ALDs). When a classroom is equipped with sound field amplification, the teacher's voice is transmitted to multiple loudspeakers mounted on the ceiling or walls. The teacher’s voice is amplified 8 to 10 dB above ambient room noise. This allows all the individuals, regardless of seat location and the direction the teacher is facing, to hear the teacher clearly.

The benefits of improved signal-to-noise ratios have been demonstrated for all students. It is not, however, sufficient amplification for a student with moderate to severe hearing loss. In that case personal amplification is needed. Careful adjustment of such systems may be necessary to avoid “feedback”; i.e., the piercing "squeeling" that occurs when sound from the loudspeakers finds its way back into the microphone

Research on sound field amplification (http://www.customallhear.com/resources/stud28.htm) in classroom systems indicates:

• Improved student attention
• Improvements in verbal and analytical performance on standardized tests
• Reduced referral for individual resource assistance
• Reduction in vocal strain for the teacher

There are numerous vendors including Hear It at http://www.hearitllc.com and Light Speed at http://www.lightspeed-tek.com.

FM System. This is another type of amplification where an FM system is worn by the listener and he receives speech input directly from the speaker who wears a microphone. These may be used in conjunction with a hearing aid, if necessary. There are numerous vendors including Phonic Ear, http://www.phonicear.com and Williams Sound, http://www.willimassound.com. There are also a number of resellers who carry products from more than one company, such as LS & S Group, Inc. (1-800-468-4789, http://www.lssgroup.com.)

Personal Amplification. If a person requires a hearing aid, it will be individually prescribed by an audiologist.