ADAAG Manual

Audio Induction Loop

This system uses a wire loop to receive input from a public address system or microphone and transmits sound by creating a magnetic field within the loop. Listeners must be sitting within the loop and have either a receiver or a hearing aid with a telecoil. Receivers can be connected to a variety of coupler types and are compatible with all loop systems. Loop systems are readily integrated with conventional sound systems and relatively easy to maintain. The loop may surround all or part of a room and can be permanently installed in the ceiling, floor or walls of a room. Portable systems are also available.

Since the signal created is, in a sense, electromagnetic interference, multiple loop systems can easily interfere with each other and are susceptible to interference from electrical wiring, computer monitors, transformers, and unshielded fluorescent lighting. In addition, the loop can also cause hum in electrical devices not shielded from electromagnetic fields, like a nearby cassette tape player. Also, construction steel in a building may cause erratic coverage (steel can absorb the magnetic fields, causing fluctuating reception). There is a new technology known as a 3-D mat that can be used instead of the conventional induction loop. There is very little spillover with 3-D mats and they are less susceptible to electromagnetic interference.

Consistent and uniform coverage is sometimes difficult with wire loops (although not with 3-D mats), depending on the application and the relative position of the listener. A listener's seating position and shifting can influence reception, making it better or worse. Moving the receiver position just a few inches can sometimes correct the reception.