Assistive Listening Devices

T-coils are a secondary pick-up device that sits inside your hearing aids. Not all hearing aids contain T-coils, but they are common. They were initially invented to help hearing aid wearers hear the telephone better. The T-coil is engaged instead of the microphone in your hearing aids. The T-coil does not pick up mechanical sound in the environment, but electromagnetic sound from the speaker coil inside the telephone’s speaker. This allows you to hear the telephone more clearly while blocking out background noise.

Manufacturers quickly realized that the T-coil could be used for much more than the telephone. Until Bluetooth became common in hearing aids, T-coils were the most common means of wireless connection for hearing aid wearers. While Bluetooth is often a superior means of connection these days, T-coils still have their advantages. Because they are a completely analog connection, they tend to maintain their connection more reliably. There is also no latency in the transmission, meaning you hear the sound instantaneously, rather than with a delay due to digital conversion.

Loop systems utilize your hearing aids’ T-coils to pick up the magnetic signal from a loop of wire. This loop typically runs around the perimeter of a space, allowing hearing aid wearers inside to pick up whatever audio signals are transmitted through the loop. At its simplest, a loop system is nothing more than a stereo receiver feeding a loop of magnetized wire rather than a speaker. Professionally installed systems tend to use more specialized amplifiers.

You will find loop systems in museums, lecture halls, houses of worship, theaters, and more. They are common in public spaces since they can provide signals to any number of hearing aid wearers inside their perimeter, provided those wearers’ hearing aids have T-coils activated. You can also have loop systems installed in various rooms in your home, or even in your car!

Similar to loop systems, FM systems transmit sound via FM radio waves instead of a loop. They may transmit to receivers that actually have a loop system in them, which is then worn around the hearing aid wearer’s neck to provide a signal to the hearing aids’ T-coils.

FM systems are common in many of the same spaces as loop systems, but are also more common in smaller classrooms, meeting rooms, and other spaces where a more portable system may be desired.

These work a lot like FM systems but transmit signals via infrared light instead of radio waves. Because they use light, they need a visible path to their receivers, and cannot pass through walls. This makes them especially suited to spaces where privacy is key, such as courtrooms.

Manufacturers usually have a few options available for different applications, such as table-top, hand-held, and lapel microphones. These will have a direct connection to your hearing aids, usually via Bluetooth. You can place these microphones near a speaker in a meeting, or hand one to your partner while you’re at a crowded museum together, and their voice will sound as though they’re standing right next to you, though they may be 20 feet away.