What is a hearing loop?
Simply stated, a hearing loop is a wire installed on the floor around the perimeter of a room or listening area. The audio feed of an installed audio system is amplified into this loop and it generates a electromagnetic field. Anyone with a T-Coil enabled hearing aid or a loop receiver can sit within the 'looped area' and wirelessly pickup the transmitted audio signal. For the listener, this gives a very direct audio link with someone speaking on a microphone, singing in the choir or playing an instrument.
More information and statistics about hearing loops can be found in this article
Churches are keeping the hearing-impaired in the "loop", click for more information.