A General Review of Assistive Listening Systems

Curtis Dickinson
Copyright 2000

ALL QUALITY ASSISTIVE LISTENING SYSTEMS (ALS) WILL:

1. Provide better word discrimination.
2. Allow personal amplification control
3. Work with or without hearing aids
4. Allow users to sit anywhere
5. Let the HOH user select ear gear
6. Comply with the Americans with Disabilities Act (Houses of religion are exempt)
7. Have little or no maintenance needs
8. Allow any number of HOH people to simultaneously use the system

THE THREE MAIN TYPES OF TECHNOLOGY

• Audio Induction Loop
  
• FM System
  
• Infrared System

Audio Induction Loop

How It Works: Unobtrusive wire circles perimeter of listening area. Can be installed under floor or in ceiling during construction.

Advantages:

• User needs only telecoil in hearing aid--position yourself anywhere within the loop!
• Can be used by itself or it may be integrated into existing PA system
• Practically no maintenance!
• Receivers can be plugged into a recorder for recording purposes

NOTE: If the user's hearing aid does not have a telecoil, a loop receiver can be used.

Disadvantages:

• Laying wire is labor intensive-but once in place-no maintenance!
• Possible interference (electromagnetic spill) and dead spots
• There is spillover of signal. This means you cannot put a loop in adjacent room. (However there is a "3-D" loop mat that overcomes this problem.) On the other hand, this allows a greater number of people to access the loop!
• Lack of standards for telecoil performance and positioning

Typical Use-Commercial: Classroom, Meeting Area, Theater, Church and Temple, Conference Room, Public transportation vehicles.
Residential use: TV, VCR, Workout room, Kitchen table, group meeting,

COST: $375 to $2,400 and more
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FM System

How It Works: A speakers voice is sent through the air by talking into an FM
microphone (transmitter) which is picked up by the listener wearing an FM
Receiver. The receiver has a volume control and earbud for the user. The
distance between the transmitter and receiver can be up to 500 feet.
Choose headphones, earbuds, Stethoscope and also via telecoil-neckloop,
silhouette. Or Direct Audio Input (DAI)

Advantages:

• Can sit anywhere.
• Can be sitting in another room.
• Can be used with telecoils.
• Portable
• Simultaneous multi-lingual capability.
• Can be used by itself or it may be integrated into existing PA system.
• Allows any number of users.
• Receivers can be plugged into a recorder for recording purposes.

Disadvantages:

• Possible to receive interference. (A channel selection switch remedies this problem)
• Others with a receiver set to the same channel, can eavesdrop

Typical Use-Commercial: Tour groups. Outdoor events, Classroom, Meeting Area, House of Religion., Museums.
Residential use: Horse back riding, in the car, restaurant, hiking.
chatting, TV.

COST: $975 to $3,000 and more
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Infrared System

How It Works: An Infrared transmitter is given a sound by a microphone. That sound is carried throughout the room waiting to be heard by a user with a receiver. The receiver acts as an amplifier-has a volume control. Choose headphones, earbuds, Stethoscope and also via telecoil-neckloop, silhouette. Or Direct Audio Input (DAI)

Advantages:

• No leaking through non-porous walls
• Can be used in adjoining rooms without interference
• Provides security from those outside the room
• Works by itself (stand-alone) or can be integrated into existing PA systems
• Will not conflict with address/paging/communication systems used to address personnel in, say, a live theater

Disadvantages:

• Can't be used in bright and direct sunlight
• New type "efficiency" ballast from fluorescent lights may cause interference. (switching channels will solve that problem)
• Set-up is labor intensive. (Though this is changing with improved design)

Typical Use-Commercial: Confidentiality (court room), Live theater (no
interference with the in-house radio transmitting), Church and Temple,
Auditorium, TV.

COST: $1,180 TO $3,000 AND MORE

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