Audio Induction Loop

Audio induction loop systems, also called audio-frequency induction loops (AFILs) or hearing loops, are an aid for the hard of hearing. They are a loop of cable around a designated area, usually a room or a building, which generates a magnetic field picked up by a hearing aid. The loops carry baseband audio-frequency currents; no carrier signal is used. The benefit is that it allows the sound source of interest—whether a musical performance or a ticket taker's side of the conversation—to be transmitted to the hearing-impaired listener clearly and free of other distracting noise in the environment. Typical installation sites would include concert halls, ticket kiosks, high-traffic public buildings (for PA announcements), auditoriums, places of worship, and homes.

In the United Kingdom, as an aid for disability, their provision where reasonably possible is required by the Equality Act 2010 and previously by the Disability Discrimination Act 1995, and they are available in "the back seats of all London taxis, which have a little microphone embedded in the dashboard in front of the driver; at 18,000 post offices in the U.K.; at most churches and cathedrals", according to Prof. David G. Meyers.

In the United States, an older technology using FM transmission to "neck loops" is more established. In comparison, hearing loops require a greater initial investment, but offer greater convenience and avoid the social stigma entailed by the FM system's paraphernalia.

An alternative system used in theatres uses invisible infrared radiation; compatible headsets can pick up the modulated infrared energy to produce sound.

This article considers the history and theory of induction loops, and some practical considerations.