An Assistive Listening Device (ALD) is any device or product, including hearing aids, which improves or “assists” hearing. All individuals can benefit from ALDs, not just persons with hearing impairment. Assistive listening devices are typically used for specific listening environments. They are commonly used in theaters, at church, in conference rooms during meetings, in schools or with televisions and radios. Some ALDs work together with hearing aids, but many can be used without hearing aids.
“FM Systems,” as they are commonly called, have the ability to increase the volume of a particular sound source (such as a public speaker, entertainer, teacher or a television, radio or stereo) and deliver it directly to an individual without also increasing the amount of background noise, regardless of the amount of distance that exists between speaker and listener or the amount of reverberation present. (Reverberation refers to sound echoes produced as sound travels, bounces or reflects off of various surfaces).
FM Systems improve the signal-to-noise ratio, which means that the level of speech or desired sound source is louder than the level of noise in the room or environment. For example, in a typical classroom setting the noise level is often nearly as loud as the voice of the teacher, making it difficult for a hearing impaired child to hear and understand well. The teacher’s voice can be heard much better with an ALD because it reduces or controls for factors such as distance, background noise and reverberation.
Personal Listening Systems usually consist of FM Systems (also called Auditory Trainers) or Pocket Talkers. Typically, personal listening devices are used in classroom settings, in small group discussions or meetings and in any other situation where an individual’s voice needs to be amplified directly to the listener (nursing homes, automobiles and restaurants). FM Systems work by transmitting or broadcasting a signal on a particular FM radio frequency (comparable to a miniature FM radio station) to a wearable radio receiver. The speaker (often a teacher) wears a lavalier (lapel) clip or headset-type microphone that is connected to a body-worn trasmitter that looks like a little box or large pager.
• Walkman-style headphones
• Ear buds that insert into the ears
• Button transducers that snap onto personal earmolds
• Silhouette inductors
• Induction loop or neck loop
• Direct audio input (“boots” that fit onto a behind-the-ear style hearing aid)
Your audiologist will work with your school to ensure that the signal from the child’s FM system will not compete with other systems in the same building.
Some schools provide Soundfield FM systems which benefit all students, not just hearing impaired students. A soundfield system works the same way as an FM System, but delivers the sound through speakers set up throughout the classroom. FM systems are commonly recommended for children with hearing impairment, auditory processing disorders, unilateral hearing loss, attention deficit disorder and sometimes autism.
This type of ALD is compatible with hearing aids. A component inside the hearing aid (usually a telephone coil) along with a boot or shoe that fits onto the hearing aid, or an induction loop that is worn around the neck allows for hook-up to a TV, radio/stereo, microphone, CD player, FM system or other assistive device. Induction loops can be used by patients with hearing aids that are equipped with a t-coil. Patients typically wear the loop around their neck, but can loop the wiring around their television room.
Special cables are typically wired or “looped” around certain auditoriums, theatres, places of worship and other public places. These cables emit an electromagnetic signal that is then sent to the person’s ears either 1) by wearing a receiver such as headphones, earbuds or 2) by wearing an individual hearing aid switch in the “T” position (telecoil option) or with a “neckloop” with the hearing aid switch in the “T” position.
Like an FM System, this provides enhancement of the speech signal or music because the signal is amplified and delivered directly to the listener, overcoming problems of distance, reverberation and background noise. Some places provide this service free of charge, while other places may charge a rental fee for the receiver.
Many systems are available to improve the signal-to-noise ratio of the television (or radio/stereo) over other environmental or background noise. Users can increase the volume they hear to a desirable level without having to turn up the TV until it becomes too loud for others in the room. One popular version of this type of ALD is called TV Ears and is available from your ACENTA audiologists.
Some telephones have a specially-designed receiver that amplifies sound. Another option is to purchase a special amplifier that has a volume wheel and is designed to work with a regular telephone. Most standard telephone receivers have an amplifying coil inside which is compatible with a hearing aid that is equipped with a telephone coil (t-coil) inside. On most behind-the-ear hearing aids, patients can switch the hearing aid to the “T” position. This activates the built-in telecoil and picks up the telephone signal without causing feedback (whistling) or interference from background noise. Some cell phones are not compatible with t-coils and we recommend that you check with your phone’s Cellular Service or cell phone manufacturer to determine which models are most compatible with hearing aids.
This type of ALD uses light waves that are invisible to the eye to carry the signal instead of FM radio waves as with the FM System discussed above. The sound signal is picked up by a wireless microphone or hardwire set-up to an amplifier transmitter that puts out infrared light waves. The receiver, typically headphones or earbuds, turns the signal into sound much like with an FM System receiver. Infrared Systems are commonly used in personal listening devices available in electronics or department stores. They are also used in large areas such as meeting halls, theatres and churches. The TV Ears ALD also uses infrared light.
• No concern about electromagnetic interference
• No concern about accidentally picking up a signal from another source (as with an FM System) since light waves do not pass through walls
• Excellent sound quality
• Personal systems can be portable (i.e. you can take your TV Ears set-up to a friend’s house or when traveling and easily use it there too)
• Cannot be used outdoors or in rooms that receive a lot of natural sunlight because sunlight will interfere with the infrared signal
• The light beam will not be received by the listener if anything physically blocks it, for example, if someone walks in front of the listener, or if the listener turns around and faces away from the light emitter.Assitive Listening Devices can also include:
• TTY/TDD (telephones for the hearing impaired that utilize typed messages)
• Closed captioning (words appearing on a screen, such as your television, that let you read what is said, rather than having to rely solely on hearing and lipreading)
• Pocket Talkers (personal amplification system equipped with a microphone and headphones or earbuds)
• Vibrating devices that can be placed under mattresses or pillows to awaken hearing impaired individuals
• Flashing lights or lamps to indicate when the phone or doorbell is ringing
• Amplified alarm clocks
• Signal alerting devices