Audio induction loop

Audio induction loop systems, also called audio-frequency induction loops (AFILs) or hearing loops, are an assistive listening technology for individuals with reduced ranges of hearing.

A hearing loop consists of a physical loop of cable or an array of looped of cables which are placed around a designated area, usually a room or a building. The cable generates a magnetic field throughout the looped space which can be picked up by a hearing aid, cochlear implant (CI) processors, and specialized hand-held hearing loop receivers for individuals without telecoil compatible hearing aids.

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 include concert halls, ticket kiosks, high-traffic public buildings (for PA announcements), auditoriums, places of worship, courtrooms, meeting rooms, 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 alternative technology using FM transmission to "neck loop" receivers was more widely adopted due to economic advantages. In comparison, hearing loop systems require a greater initial investment by the facility operator, but offer greater convenience and avoid the social stigma and hygienic concerns entailed by the FM system's paraphernalia for those who have hearing aids.

Another alternative system, used primarily in theatres, uses invisible infrared radiation; compatible headsets can pick up the modulated infrared energy to reproduce sound.

The pickup coil in a hearing aid is known as a telecoil (or T-coil) because its early form was to pick up a magnetic field from coils within a telephone. These were included as a part of the method of enabling a two-way conversation over a single pair of wires. The telecoil enabled hearing aid users to hear the phone conversation more clearly without also picking up background noise around them.

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