A well designed and installed hearing loop system sends the audio signal directly to any hearing aid, cochlear implant, or receiver with a telecoil. No background noise, no reverberation, just clear sound.
How hearing loops work
Hearing loop technology, sometimes known as an audio induction loop systems, audio-frequency induction loops or hearing loops, are an assistive listening technology for individuals with reduced ranges of hearing.

“Churches put Hearing-Impaired in Loop”, Chicago Tribune, July 3, 2010
Reprinted with permission Alex Bordens and Phil Geib/Tribune
Watch this short video to see how hearing loops works:

Video courtesy of OTOjOY