Assistive Listening Devices (ALDs) improve the listener’s ability to understand by bringing the source of the sound closer to the listener. These devices reduce the negative effects of background noise and distance by using different types of signals to transmit the audio information from the speaker to the listener. The listener can usually amplify the volume of the sound source without amplifying the background noise.
Overviews of ALDs are available from websites provided by several different organizations:
St. John's Medical Center's Pediatric Audiology Project in Jackson Hole, Wyoming put together a great video that shows the potential consequences of unmanaged hearing loss in the classroom - Hearing Loss in the Classroom.
A Frequency Modulation (FM) system includes a microphone/transmitter used by the speaker and a receiver used by the listener. The audio signal is transmitted by radio waves using different channels (frequencies). FM systems can be used for one-on-one meetings and in large group settings. These systems are often found in classrooms, theaters, public meeting places, and places of worship.
"Samantha and her Fun FM and Hearing Aid Book!" - created by a young deaf girl as a way to explain the use of her hearing aid and FM system to her classmates
Infrared systems transmit sound using infrared light waves. These systems are often used with TV sets and large group settings.
Induction loop systems are most commonly used in large group areas. For this system, an induction loop wire is installed around the area, often on the floor, and is connected to the speaker’s microphone. Listeners often use the telecoil in their hearing aid or cochlear implant to receive the signal. HearingLoop.org provides an overview of induction loop systems.
Listen to a simulation! - HearingLoop.org demonstrates a simulation of the telecoil option on a hearing aid and an induction loop versus the microphone option on a hearing aid and no induction loop, please click on the "M" and the "T" in each picture.
Personal communication devices are used for one-on-one communication. The speaker uses a microphone connected to the PCD device which amplifies the sound. The audio signal is sent directly to the listener’s headset or hearing aid.
Sound field amplification systems amplify and broadcast the speaker’s voice through loudspeakers.