Assistive listening technologies are devices to help the deaf and hard of hearing participate in everyday communication, according to the American Speech-Language-Hearing Association. These specialized devices are used in addition to hearing aids to undo the negative effects of poor acoustics and background noise. Audiologists have special training allowing them to assist the hearing disabled in choosing the best device.
Listening Devices
The hearing disabled can find it difficult to hear in large group situations such as classrooms, lecture halls, conference rooms, churches or live theaters. Personal frequency modulation, or FM, systems transmit sound from the speaker's microphone to an FM receiver and from there to the user's hearing aids. Induction loop systems are another technology used in group situations. The induction wire is connected to the speaker's microphone and when the hearing aid user switches to the hearing aid's telephone "T" setting, the telecoil within the hearing aid picks up the microphone signal. Adjusting the volume of the hearing aid adjusts the volume of the speaker.
Alert Devices
Audible alert devices, such as telephones or smoke alarms, are not useful to a person with profound hearing loss. Manufacturers have developed specialized alarms that use flashing lights or a vibrating device. Many alert systems wirelessly tie into a universal receiver that the user carries with him, puts under the pillow or attaches to the bed. Some receivers allow programmable patterns of flashing lights or vibration for each device. Light and vibrating alerts are available for doorbells, smoke alarms, weather and emergency alerts, telephones, motion sensors, alarm clocks, baby monitors and doorway mats.
Captioning
Captioning is a synchronized text display of spoken words. Closed captioning is an option available on all televisions since 1993 and most TV shows since 1996, according to the Federal Communication Commission. Movies on DVD have captioning as a subtitle option in the menu language settings. Movie theaters have incorporated captioning by reflecting a reverse-text display from the back of the movie theater to an acrylic panel in front of the patron. Other theaters hold special movie screenings with open captions, which are similar to subtitles. Since this requires a special print of the film, the availability of open caption movies is limited.
Telephone Devices
TTY, or teletype, devices work over the telephone lines to allow text conversations. The user types and reads conversations using the device. Businesses and government agencies publish separate TTY compatible phone numbers for the deaf. Hotels in the United States use TTY devices to make the room accessible to hearing impaired guests. Text messaging with cell phones provides an alternative to the TTY for friends and family.
