Assistive Listening Devices

What are Assistive Listening Devices (ALDs)?
Assistive Listening Devices (ALDs) are amplification instruments that are designed to be helpful in specific, but not all listening situations. For instance, there are ALDs that amplify the TV, the telephone, that amplify in theaters, in places of worship, and that amplify public speakers. Hearing aids, which also amplify sound, are instruments that can be used in all listening situations. But because a hearing aid is an all-purpose instrument, it may not be as successful in each and every specific application.

How do ALDs differ from hearing aids?
The construction of an ALD is different from a hearing aid in one important aspect. All of the components of a hearing aid, the microphone, the amplifier, and the loudspeaker are located within the body of the instrument that is placed on the user's ear. Therefore, the microphone of a hearing aid picks up both signal and noise. In contrast, the microphone of an ALD is separated from the body of the instrument and is placed at the sound source so that it picks up the desired signal and reduces the interference of background noise. This is the biggest advantage of ALDs.

How do ALDs transmit from source to receiver?
The method that is used to send the signal from microphone (transmitter) to receiver is the most important factor that distinguishes the various types of ALDs. There are five primary methods that are used.

• Hard Wired:
  A thin cable from the receiver attaches the microphone. This type of ALD is useful for one-to-one conversation such as while traveling in a car.
• FM:
  The signal is transmitted by an FM radio signal. An FM system is often used in classrooms for the hearing impaired. FM systems can be used in addition to hearing aids and are especially helpful to reduce background noise levels.
• Infrared:
  The signal is transmitted by an infrared light signal, similar to the remote control on TVs or VCRs. An infrared system is often used in the home to amplify the TV or in movies, theaters, or public speaking situations. The infrared system requires a clear line-of-sight from the transmitter to the receiver.
• Loop:
  The transmitter is attached to a loop of wire that is placed at the perimeter of the room. The loop of wire generates an electromagnetic field that is picked up by the receiver. This system is also used in classes for the hearing impaired or while watching TV at home.
• Bluetooth
  Bluetooth technology can be incorporated into hearing aids to offer hands-free mobile phone use. Bluetooth can also be coupled to work with your TV or MP3 player.

When should you consider using an ALD?
An ALD should be considered when you have difficulty in a specific, but not all situations. For instance, if you like the TV louder than your family, an infrared, FM, or loop system would allow you to solve this problem. A microphone is placed in front of the TV loudspeaker (attached with Velcro) and is connected to the transmitter. Your family would adjust the loudness of the TV to their comfort; you would adjust the loudness of your receiver to your comfort. In this way, the specific problem of TV viewing is solved. If you have difficulty in a number of different situations, you should consider a hearing aid instead of an ALD. You also may use an ALD with your hearing aid to enhance the performance of the hearing aid.

Website links for Assistive Listening Devices

• Phonak www.phonak.com
• Adco Hearing Products www.adcohearing.com
• Phonic Ear FM and Assistive Devices www.phonicear.com
• T.V. EARS www.tvears.com

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