Loop Systems – Dr. Juliette Sterkens

What do Westminster Abbey, the Opera House in Sydney Australia, the main chamber of the US House of Representatives and the Oshkosh Convention Center have in common?

They all have hearing loops installed.

Purpose of an Induction Loop

A hearing loop helps persons who use hearing aids that are equipped with T-coils hear sounds from a PA system directly and clearly in the hearing aids, because it reduces or cuts out background noise.

How Loop Systems Work

A hearing loop provides a magnetic, wireless signal that is picked up by the hearing aid when it is set to ‘T’ (Telecoil) setting. The loop system consists of a microphone to pick up the spoken word; an amplifier which processes the signal which is then sent through the final piece; the loop cable, a wire placed around the perimeter of a room or sanctuary to act as an antenna that radiates the magnetic signal to the hearing aid.

When a hearing aid user selects the ‘T’ setting; he or she can pick up the sounds spoken into the PA system’s microphone instead of the hearing aid’s internal microphone. This results in improved speech understanding because the listener receives a clear signal without any background noise.

Hearing Loops Interact with Hearing Aids

Digital hearing aids have significantly improved in the last decade, but they still do not restore hearing to normal. What most hearing aid users need is an improved signal to noise ratio (or SNR) of +10 or greater. This is difficult to attain in reverberant places, such as auditoriums or churches, resulting in the typical “I can hear but not understand!” complaint. Hearing aids equipped with T- coils can help reduce this problem.
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When a hearing aid is set to “T”-coil, the instrument becomes a personalized speaker in your ear for the sounds that are picked up by the microphone of the PA system. That way sounds are heard clearly, without distortion or background noise pick-up.

Many Hearing Instruments Are Equipped with T-Coils

Most behind the ear hearing aids, and all but the smallest of custom in-the-ear instruments, can be equipped with a T-coil. Some-times this T-coil is installed inside your instrument but not activated. Another option is the Mic plus T-coil setting or MT. This setting lets you hear a combination of sound all around you and the hearing loop.

How to Know if Your Hearing Aid is Equipped with a T-Coil

The T-coil program is accessed by a push button on your hearing aid or via the use of a remote control. Audiologists often recommend this T-coil setting for listening on the telephone without whistling. Sometimes the T-coil is installed but not activated.

If your instrument has a push button allowing you to access a so-called “telephone program” where the microphone is turned off and you were instructed can use it on the phone without whistling, you most probably have a t-coil.

The Difference Between the T and MT Program

When you switch your hearing aid to “T” setting, the hearing aid’s microphone is switched off. This allows you to only hear the signal from the hearing loop or listen on the phone, while reducing background noise and eliminating feedback (whistling).

When your instrument is set to “MT” you will hear a combination of sounds around you (picked up by the microphone) and signal from the “T-coil”. The MT position is provided on some hearing aids and can be used while watching TV in your home (if equipped with a home loop) or in church as it allows you to hear the person sitting beside you and hear the signal from the hearing loop.

What Can Go Wrong with a T or MT Setting

The new lighting and today’s flat screen monitors rarely have an influence on induction loops. Occasionally T-coils are susceptible to interference (low pitched buzzing) around malfunctioning or older fluorescent lights, conventional CRT (non-flat screen) computer monitors, electrical wires, dimmer switches and transformers. Let us know if this happens as reprogramming your instruments usually takes care of this.

Using Hearing Loops with Heart Pacemakers

Under normal circumstances, a correctly installed induction loop system does not interfere with heart pacemakers. A minimum separation distance of 2 inches (50mm) should be maintained between loop cable and pacemaker to remove any potential for interference.