A relatively inexpensive "hearing loop" - "a thin strand of copper wire radiating electromagnetic signals that can be picked up by a tiny receiver already built into most hearing aids and cochlear implants" - installed in the floor around the edges of a room can transmit the signal from a microphone directly to the receiver, called a telecoil, or t-coil.
Hearing aids work best in relatively quiet places, where there are few sources of noise. In a subway or other crowded, busy place, hearing aids amplify all of the noise indiscriminately, creating a true cacophony from which it is difficult to distinguish the sounds that matter. The hearing loop / telecoil combination solves that problem, at least at events where microphones are used.
The technology "has been widely adopted in Northern Europe" and is catching on in the U.S.
Could it have a down side? I suppose so, but I don't see it.
Ken Pimple, PAIT Project Director