Listening Devices: Part 3- Assistive Listening Devices

Assistive Listening Devices (ALDs) are used in conjunction with a hearing aid or cochlear implant. They help the user in specific listening situations such as in a lecture hall or in a noisy restaurant, where the hearing aid or cochlear implant are not adequate.

When ALDs May Be Needed
If there is an excess of any or all of the following:

• Ambient Noise: noise that is present in a room when it is unoccupied such as open windows, buzzing lights, or piped-in music.
• Reverberation: Echoes caused by high ceilings, hardwood floors, or unadorned plaster walls.
• Background Noise: Noises other than what the user wants to hear such as rustling paper, shuffling feet, extraneous conversations occuring in a classroom while the teacher is talking. 

Types of ALDs

• Wireless Systems
• FM System- utilizes radio waves to transmit sound from the source to the user.
• Personal FM trainer: The speaker wears a microphone and the sound is transmitted directly to the user's receiver
• Sound-field FM system: The speaker wears a microphone, but the sound is transmitted by loudspeakers that are positioned throughout the room.

• Infrared System- similar to FM systems, but use infrared signals instead. The signals cannot travel through walls, affording more privacy.
• Induction Loop Systems- A room is looped with a wire that broadcasts electromagnetic energy. This is picked up by a hearing aid when the telecoil is activated. Some cochlear implants are also able to benefit from looping.

• Hardwired Systems- These connect the sound source to the listener by actual wire. They are most often used for listening to television, radio, or music.They have the disadvantage of requiring the listening to be tethered to the sound source.

Other Technology

There are many other products available to people with hearing loss. These are useful in situations when the person is not wearing his/her hearing aid or cochlear implant, such as while sleeping.

• Vibrating or flashing alarm clocks
• Doorbells hooked to lamps that flash when it is rung
• Flashing light smoke detectors
• Telephone ring signaler that causes a lamp to flash
• Text display systems for telephones
• Closed captioning for TV and movies