Whereas standard behind and in-the-ear hearing aids work well in relatively quiet, more intimate settings, these devices often lose their effectiveness in larger, public spaces where background noise puts the hard of hearing at a disadvantage. Although the technology to solve this problem has been available for years and widely used in Northern Europe, implementation has lagged in the US, because not enough is being done to promote their use.
Induction-loop systems, also called “hearing loops,” capture electromagnetic waves produced by a microphone, public address systems or telephone receivers and broadcasts these signals directly to the hearing aid in a person’s ear, provided that it is equipped with a tiny copper telecoil wire that can pick up the signal. A hearing loop could be as small as a piece of wire worn around the neck (called a neck loop) or as large as a ring of cable placed around the perimeter of a room or space.

Normally, a hearing aid captures sound with its microphone then amplifies this sound for the wearer.
A hearing aid equipped with a telecoil can cut through ambient noise by shutting off the normal microphone, enabling the wearer to tune in directly to the sounds being broadcast. Telecoils work somewhat like Wi-Fi for hearing aids, enabling them to serve as customized, wireless loudspeakers, says David Myers, a psychology professor at Hope College in Holland, Mich., and creator of HearingLoop.org.
Hearing aid makers are increasingly equipping their devices with telecoils. Today more than 60 percent of hearing aids now come with telecoils, up from 37 percent in 2001.

Written by Larry Greenemeier of Scientific American