Table A2

Summary of Assistive Listening Devices and Systems

COMPARISON OF LARGE AREA ASSISTIVE LISTENING SYSTEMS
System Description Advantages Disadvantages Typical Applications
FM BROADCAST
(40 frequencies available on narrow band transmission systems. Ten frequencies available on wideband transmission systems.)
Transmitters: FM base station or personal transmitter broadcasts signal to listening area.
Receiver: Pocket size with:

a)earphone(s), or
b)headset, or
c)induction neck-loop or silhouette coil coupling to personal hearing aid equipped with telecoil, or
d)direct audio input (DAI) to personal hearing aid.

Highly portable when used with body-worn, personal transmitter.

Easy to install.

May be used separately or integrated with existing PA-systems.

Multiple frequencies allow for use by different groups within same area (e.g., multi- language translation).

Signal spill-over to adjacent rooms/ listening areas (can prevent interference by using different transmission frequencies for each room/listening area). Choose infrared if privacy is essential.

Receivers required for everyone. Requires administration and maintenance of receivers.

Susceptible to electrical interference when used with induction neck-loop/silhouette (Provision of DAI audio shoes and cords is impractical for public applications).

Some systems more susceptible to radio wave interference and signal drift than others

Service counters

Outdoor guided tours

Tour busses

Meeting rooms

Conference rooms

Auditoriums

Classrooms

Courtrooms

Churches and Temples

Theaters

Museums

Theme parks

Arenas

Sport stadiums

Retirement/nursing homes

Hospitals

INFRARED LIGHT
Transmitter: Amplifier drives emitter panel(s) covering listening area.
Receivers: Under-chin or Pendant type receiver with:
a) headset, or
b) earphone(s), or
c) induction neck-loop or silhouette coil coupling to personal hearing aid equipped with telecoil, or
d) direct audio input (DAI) to personal hearing aid.

Unlike induction or FM transmission, IR transmission does not travel through walls or other solid surfaces.

Insures confidentiality.

Infrared receivers compatible with most infrared emitters.

May be used separately or integrated with existing PA-systems.

Can be used for multi- language translation (must use special multi-frequency receivers).

Receivers required for everyone. Requires administration and maintenance of receivers.

Ineffective in direct sunlight.

Careful installation required to insure entire listening area will receive IR signal.

Susceptible to electrical interference when used with induction neckloop/silhouette (Provision of DAI audio shoes and cords is impractical for public applications).

Lifetime of emitters varies with company.

Historical buildings may pose installation problems.

Indoor service counters

Meetings requiring confidentiality

Meeting rooms

Conference rooms

Auditoriums

Classrooms

Courtrooms

Churches and Temples

Theaters

Museums

Arenas (indoors only)

Sport stadiums (indoors only)

Retirement/nursing homes

Hospitals

CONVENTIONAL INDUCTION LOOP
Transmitter: Amplifier drives an induction loop that surrounds listening area.
Receivers:
a)Personal hearing aid with telecoil.
b)Pocket size induction receiver with earphone or headset.
c)Self-contained wand.
d)Telecoil inside plastic chassis which looks like a BTE, ITE, or canal hearing aid.

Requires little, or noadministration of receivers, if most people have telecoil-equipped hearing aids. Induction receivers must be used where hearing aids in use are not equipped with telecoils.

Induction receivers are compatible with all loop systems.

Unobtrusive with telecoil hearing aid.

May be used separately or integrated with existing PA-systems.

Portable systems are available for use with small groups of listeners. These portable systems can be stored in a carrying case and set up temporarily, as needed.

Signal spill-over to adjacent rooms.

Susceptible to electrical interference.

Limited portability unless areas are pre- looped or small, portable system is used (see advantages).

Requires installation of loop wire. Installation may be difficult in pre- existing buildings. Skilled installation essential in historical buildings (and may not be permitted at all).

If listener does not have telecoil-equipped hearing aid then requires administration and maintenance of receivers.

Service counters

Ports of transportation

Public transportation vehicles

Tour busses

Meeting rooms

Conference rooms

Auditoriums

Classrooms

Courtrooms

Churches and Temples

Theaters

Museums

Theme parks

Arenas

Sport stadiums

Retirement/nursing homes

Hospitals

3-D LOOP SYSTEM
Transmitter: Amplifier drives a 3-D mat that is placed under the carpet of the listening area.
Receivers:
a) Personal hearing aid with telecoil.
b) Pocket size induction receiver with earphone or head-set.
c) Self-contained wand.
d) Telecoil inside plastic chassis which looks like a BTE, ITE, or canal hearing aid.

Requires little, or no administration of receivers, provided most people have telecoil-equipped hearing aids.

Induction receivers are compatible with all loops systems.

May be used separately or integrated with existing PA-systems.

Three-dimensional reception of loop signal regardless of telecoil position.

Reduced signal spillover allows adjacent rooms to be looped without signal interference.

3-D loop mats must be separated by 6 feet to avoid signal spillover.

Limited portability (areas may be pre-3-D Loop matted to facilitate portability).

Requires installation of 3-D Loop mats. Instal- lation may be difficult in pre-existing build- ings. Skilled installa- tion essential in historical buildings (and may not be permitted at all).

If listener does not have telecoil-equipped hearing aid then requires administra- tion and maintenance of receivers.

Susceptible to electrical interference.

Service counters

Ports of Transportation

Meeting rooms

Conference rooms

Auditoriums

Classrooms

Courtrooms

Museums

Theme Parks

Retirement/nursing homes

Meetings requiring confidentiality

Hospitals

Modified from a chart published by Centrum Sound, Cupertino, California
Cynthia L. Compton, Assistive Devices Center
Department of Audiology and Speech-Language Pathology
Gallaudet University, Washington, DC