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The following material about Assistive Listening Devices (ALDs) is taken from material supplied by Advocates for Better Communication, League for the Hard of Hearing, 50 Broadway, New York, NY 10004, www.lhh.org, info@lhh.org, Phone: 917-305-7700, TTY: 917-305-7999, Fax: 917-305-7888. Added comments by the UMCD Standing Committee on Church Promotion: Hard of Hearing and Late-Deafened People are in italics.
Infrared systems use harmless, invisible light beams in the infrared range of the spectrum. Infrared light emitters can be connected to the existing sound or PA (public address) system. Sound is relayed to the emitters, which are located at various points in the listening area. There are also self-contained, portable, battery-powered combination microphone amplifiers and infrared emitters. The emitters convert the acoustic signal (e.g., speech) to infrared light and transmit these light waves throughout the listening area. The light waves are picked up by a photocell on the receiver worn by the listener and converted back to sound through the earphones.
Receivers can be: 1) "Stethoscope" models connected to receivers hanging under the chin, 2) Headphones or 3) Body packs with jacks for use with earbuds for those not wearing hearing aids, or with neckloops or silhouettes for those using telecoils ("T" switches) on hearing aids. Direct audio input (DAI), which connects the hearing aid directly to the receiver via a "boot," "shoe," or plug and cord can also be used. Only infrared receivers with jacks can be used by people with cochlear implants, DAI, or hearing aids with "T" switches. A neckloop attachment is needed for use with hearing aids that have "T" switches.
Infrared assistive listening devices offer impressive clarity and intelligibility regardless of where a person is sitting. Infrared works best in a darkened room with light colored walls which makes it ideal for the theater. It does not, however, work outdoors. Infrared is also unable to penetrate solid barriers, such as walls. Line-of-sight placement of the emitters is preferred, but since IR is like light, it can bounce off reflecting surfaces and fill a room unless blocked by a solid barrier. Infrared is the only system that allows for confidential or private transmission in a closed room.
Sound coming through a microphone or PA system is fed into an FM transmitter. The transmitter broadcasts the signal to the listening area utilizing the special frequency FM radio band designated by the FCC for this use. Listeners have a personal FM receiver and earphones (or ear buds) to pick up the signal, adjusting the volume to their individual needs. Hearing aid users set their aids to the telecoil ("T") switch and wear a neckloop or silhouette connected to their individually worn FM receivers. Cochlear Implant users can use a patch cord to plug directly into the receivers. Direct audio input is also available for FM systems.
FM systems have excellent sound quality and some are completely portable. That is, the transmitter can be taken to any room for use with a public address amplifier; or that some FM systems can be purchased with portable units used by the speaker. All receivers are, of course, portable.
Users can listen anywhere within a several hundred-foot range inside and outside. However, FM transmits through walls and for some distance, so nearby rooms should use different frequencies or channels to prevent interference. For this reason, FM may be inappropriate for private or confidential use. Even though a special FM band has been established by the FCC, there may be interference from a variety of sources over these wave lengths.
A loop of insulated wire circling the listening area receives an electrical impulse from an amplifier that has been placed in a microphone or other signal source close to the speaker. In order to use the system, listeners must physically be within the loop area. A magnetic field within the loop is picked up by the telecoil ("T" switch) on the listener's hearing aid(s) or by a separate telecoil-equipped induction receiver with an earpiece and volume control. The magnetic field is then reconverted through the hearing aid to sound. Fluorescent lighting can interfere with transmission and the electromagnetic signal can spill over into adjacent areas or rooms.
Sound coming through a microphone or PA system is fed into an FM transmitter. The transmitter broadcasts the signal to the listening area utilizing the special frequency FM radio band designated by the FCC for this use. Listeners have a personal FM receiver and earphones to pick up the signal, adjusting the volume to their individual needs. Hearing aid users set their aids to the telecoil ("T") switch and wear a neckloop or silhouette connected to their individually worn FM receivers. Direct audio input is also available for FM systems.
The CM-3 conference microphone has been designed to enhance the pickup range for a wide variety of personal assistive listening devices, cassette recorders, and tapeless digital voice recorders. With CM-3, there is no need for passing the microphone around or to miss out on faint voices during play-back of the meeting recordings. Click here to learn more (link opens in new window).
Two people who helped compiled this resource report good results using the CM-3 Conference Microphones. Their experience is limited, however, so we recommend that interested parties do more research.
Examples of assistive learning devices, such as teleloop systems, infrared systems, and FM systems are on Centrum Sound's web site (link opens in a new window). This link is offered for your information only. NOTE: Other sources can be found with a little research.
Centrum Sound accepts major credit cards and offers a 30 day money-back guarantee on all standard assistive devices and accessories. They also have Demonstration Centers in many hearing aid dispensing offices throughout the United States. Please contact Centrum Sound for more information and details:
CENTRUM SOUND SYSTEMS
572 La Conner Drive, Sunnyvale, CA 94087 USA
Phone: 408-736-6500 Fax: 408-736-6552
Web Site: http://www.centrumsound.com (link opens in a new window)
E-mail: centrumweb@aol.com
