His reaction is a common one. The technology, which has been widely adopted in Northern Europe, has the potential to transform the lives of tens of millions of Americans, according to national advocacy groups. As loops are installed in stores, banks, museums, subway stations and other public spaces, people who have felt excluded are suddenly back in the conversation.

A hearing loop, typically installed on the floor around the periphery of a room, is 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. When the receiver is turned on, the hearing aid receives only the sounds coming directly from a microphone, not the background cacophony.

“It’s the equivalent of a wheelchair ramp for people who used to be socially isolated because of their hearing loss,” said David G. Myers, a professor of psychology at Hope College in Holland, Mich., who is hard of hearing. “I used to detest my hearing aids, but now that they serve this second purpose, I love the way they’ve enriched my life.”

After his first encounter with a hearing loop at an abbey in Scotland, where he was shocked to suddenly be able to understand every word of a service, Dr. Myers installed a loop in his own home and successfully campaigned to have loops installed at hundreds of places in Michigan, including the Grand Rapids airport and the basketball arena at Michigan State University.

“One of the beauties of this simple technology is that it serves me everywhere from my office to my home TV room to nearly all the worship places and public auditoriums of my community,” Dr. Myers said.