Timothy C. Hain, MD
Last modified: December 30, 2011
Loop systems and telecoils work together with hearing aids to help hard of hearing people hear better. They consist of an transmitting antenna that converts sound into radio waves, and a reciever -- the "telecoil" placed inside of ones hearing aid. This system allows you to have sound -- such as from the radio, TV, telephone, or public speaker -- sent directly to your hearing aid with greater clarity. Loop systems resemble the "blue tooth" headsets used for cell-phones, but interface with your hearing aid rather than a separate ear-transducer.
Pros and Cons.
Loop/telecoils have several big advantages over regular hearing aids:
1. No feedback !
2. You don't hear everything -- there is less noise.
You can set up personal loops for your TV or telephone. Permanent loop systems are often installed in public buildings and churches. In Europe, they are now installed in many forms of public transportation—taxis, busses, trains and ships. You will also find loop systems in most telephones, and some schools and offices where there are hard of hearing people. However, in the US, FM and IR technology systems are more common.
3. They are much cheaper than (say) buying a second hearing aid.
Loop/telecoils also have some problems over regular hearing aids
1. Telecoils pick up electrical interference. Loops produce electrical interference (mainly with other loops).
2. Except for their use in telephones (which are required to be comptable), loops require some preparation (i.e wiring).
3. Telecoils take up space, and are not available in very tiny hearing aids.
The main advantage of loop systems is that they are inexpensive ways to hear things like the telephone or TV. The main problem with them is that they may pick up hum or static from electrical equipment and wiring and also that they take up space in the hearing aid.
Loops are not a good idea for people with mild hearing problems or who want very small hearing aids.
Loops are a good idea with people who are struggling to hear, even with powerful hearing aids. FM systems are even better, but they cost more money and take up more space on your ear.
The first patented magnetic induction loop communication system was invented by Joseph Poliakoff of Great Britain in 1937. The first wearable hearing aid to incorporate a telecoil is reported to be the Multitone VPM in 1938. The use of induction loops increased and then declined as improved AM, FM and infrared technologies were developed. At the present time, loops are an inexpensive method of augmenting hearing aid performance.
Loop systems consist of three parts—a microphone or other device that produces an electrical signal that you want to hear (like a TV), a loop amplifier, and a loop of wire. Sometimes the amplifier and loop are contained within a single device (a neck-loop or a silhouette). That's the transmitting side. Your hearing aids equipped with telecoils make up the receiving side.
Audio signals are picked up by the microphone or directly (electrically) from a sound source like your TV or stereo. The electrical option is much better. They are amplified by the loop amplifier and then travel through a loop of wire that surrounds the listening area. When the sound signal travels through the loop of wire, it produces a magnetic field in the looped area that mirrors the frequency and intensity characteristics of the original sound signal.
Your hearing aid converts this signal into sound you can hear. When you switch your hearing aid from microphone to its telecoil, it connects a small coil of wire (t-coil) to the input of the hearing aid's amplifier instead of its microphone. This tiny coil of wire is sensitive to nearby magnetic fields such as the one produced by the loop system. The changing magnetic field in the room loop induces a corresponding electrical signal into the telecoil. The hearing aid amplifier then amplifies this signal and you hear a faithful reproduction of the original speech signal.
This process of inducing an electrical current in one wire as a result of current flowing in a nearby wire is called induction—hence the term induction loop system—or just "loop system" for short.
Since any electrical current will result in a magnetic field, depending on their location, loop systems can be prone to interference. This interference is usually a buzzing or humming sound. This resulting buzz or hum may be so loud that you can't use the loop system in certain places. Typically, interference can come from nearby electrical wires, fuse boxes, TVs, computer monitors and fluorescent light fixtures.
In order to tell if the area you want to loop is free from interference, you should switch on your telecoil(s), turn up the volume on your hearing aids and listen. If you hear loud buzzing, that is not a good place for a loop system. As you move around, you will notice that the interference level changes. Set up your loop system where the interference is non-existent or negligible.
Telecoils as shown here (courtesy Tibbetts Industries, Inc.), are tiny additions to hearing aids.
A telecoil is a tiny coil of wire inside your hearing aid that picks up electromagnetic signals given off by devices including loop systems and telephone handsets.
There are a variety of names by which people refer to telecoils. They may call them T-coils, T-switches, telecoils, telephone coils or audio coils.
In order to use a loop system, you must have hearing aids equipped with telecoils. Unfortunately, many hard of hearing people do not know whether their hearing aids have telecoils installed. Before you buy a hearing aid, you should consider whether or not you want telecoils installed. Because telecoils take up space, they will not be available in the tiniest hearing aids.
Currently, in the U.S., no more than 30%-40 % of current hearing aids include telecoils. Telecoils can only fit in two styles of hearing aids: In-The-Ear (ITE) and Behind-The-Ear (BTE) aids. The smaller hearing aids are not large enough to fit the telecoil.
If you do have a telecoil, your hearing aid(s) should have a three position switch (for analog aids) or three programmable modes (for digital aids). These three modes are "M" for microphone only, "T" for telecoil only and "MT" for both microphone and telecoil together.
This combined microphone/telecoil mode is important. When you have your hearing aids in the "T" mode, you can only hear what comes through your telecoils. For example, if you are in a meeting and the person sitting next to you asks you a question, you won't hear him at all. You'd have to switch your hearing aids back to the "M" setting and have the person repeat the question. In the meantime, you'll be missing anything coming through the loop system.
With the "MT" position, you'll be able to hear both through the loop system and people talking around you through your hearing aids' microphones. For example, you may be listening to your TV at home though a loop system. If it is quiet and you have your hearing aids set to the "MT" position, you can listen for the phone ringing at the same time you are hearing the TV.
Later, if there is a lot of noise around you (the kids have their TV up high), you can switch to the "T" position and cut out all the interference and just hear through the loop system. This way you can have the best of both worlds!
If you cannot get hearing aids equipped with a "MT" function, there are still good options. At home hook both a microphone and a TV, for example, into your home loop system. The loop system's microphone will pick up the kids crying, the doorbell ringing or any other sounds around you and superimpose these sounds on top of those from the TV and you will hear both though your hearing aids' telecoils.
There are several varieties of loops:
Neckloops: a necklace-size loop of wire that can be plugged into an assistive device, a radio, TV, IPOD, computers and some telephones. It is then worn around the neck of someone who has a hearing aid with a telecoil. Like all loops, it eliminates feedback.
Silhouette: a small loop of wire embedded in a thin hook-shaped piece of plastic with a wire coming out of it that can be plugged into a sound source. It is hooked over the ear and nestles beside a BTE hearing aid with a telecoil. Because they are close to the telecoil,they are much less susceptible to interference, and because they stay aligned relative to the hearing aid, they are less sensitive to head position than other types of loops.
A home-loop (we think this is the best):
For the do-it-yourself people, at home, run a wire loop around the edge of a room—stringing it over doorways or you can place it under the edge of a carpet. Hook both ends of the loop wire to the loop amplifier.
To set up a loop system once it is wired, plug the loop amplifier in, plug the input device or microphone into the loop amplifier, and switch your hearing aid over to the t-coil mode.
When using telecoils, if you tilt your head while listening to a room loop the sound changes in volume. If there is a strong loop signal, this may not matter at all—especially if you have amplified telecoils (telecoils with a tiny amplifier attached inside the hearing aid). However, if you are sitting where the signal is weaker, you may notice that you hear better with your head held at a certain angle. Experiment—tilt your head at different angles and discover the best angle at which to hold your head for the strongest signal.
The same thing can happen when using a phone. How you hold a phone up to your telecoils can affect how loud you hear the person talking. Some people must place the ear-piece slightly behind their ear rather than directly over the ear. This varies with the phone and also the placement of the t-coil in the hearing aid.
Home loop system equipment, as shown in the table below, is relatively inexpensive—in the neighborhood of $200.00.