Audio Loops

Loop Systems-The Best-Kept Secret in Town!

courtesy of Pure Direct Sound © March 2004 by Neil Bauman, Ph.D.

Question: Every once in a while I hear hard of hearing people talking about "loop systems." What are loop systems? How can they help hard of hearing people hear better? Are they expensive?-D. B.

Answer: Good questions. Glad you asked them. Loop systems are truly wonderful. They let hard of hearing people hear ever so much better, especially in group settings where they can't get close to the person speaking. For some reason, even though loop systems give wonderful sound and are cost effective, they seem to be one of the best-kept secrets around. Few hard of hearing people have even heard of them. Listen up. I'll let you in on this nifty secret.

Loop systems are a class of Hearing Assistive Technology (HAT)/Assistive Listening Devices (ALDs) that work together with hearing aids to help hard of hearing people hear better. Other classes of ALDs include such things as Personal Amplifiers (PockeTalkers), FM systems and infrared systems. Unlike the above systems, you do not have to wear anything extra in order to connect to, and use, a loop system-no neckloops, wires, silhouettes, receivers or headphones. All you need are your hearing aids equipped with telecoils.

Loop Systems Can Do All This and More Imagine being able to hear your TV or stereo from anywhere in your house as you move from room to room-and the sound stays exactly the same-sounding as if a person is talking directly into both your ears at the same time. A home loop system can do this for you. Also, you can hook your home phones into your loop system so you can hear on any phone in the house with both ears, whether the phone is amplified or not. In fact, you can put any signal you want into a loop system. In addition to your phone, that may be your TV, radio, stereo, computer, doorbell or whatever produces a sound you want to hear. You can even set up a portable loop system outside on the grass for an outdoor meeting or family gathering.

Did you ever dream of riding in your car and hearing the radio clearly without road noise intruding, or clearly hearing the people in the back seat? This dream can come true if you loop your car (or motor home or boat).

Do you wish you could go to a public meeting or church service and hear the speaker/minister as clearly as if he were talking right into your ears-no matter where you are sitting-without having to hook yourself to some ALD? Loop systems will do this too.

With loop systems you don't have to fuss around, hooking yourself up with wires, neckloops, silhouettes or headsets to some ALD receiver. Furthermore, there is no extra paraphernalia to lug around, nor do you have to worry about batteries dying at the most inopportune times and not having fresh ones with you.

Furthermore, loop systems will accommodate as many people as can sit/stand inside the loop-all without any extra equipment or cost. Therefore, with loop systems, you never have to worry about there not being enough receivers to go around.

Did you ever get to a meeting late and find all the chairs at the front were taken so you had to sit at the back where you couldn't hear? If the room is looped, this is not a problem-just switch to your hearing aids to their telecoils and you will be able to hear loud and clear from the very back row.

You can use loop systems almost anywhere. Typically permanent loop systems may be installed in various meeting areas such as public buildings and churches. In Europe, they are now installed in many forms of public transportation-taxis, busses, trains and ships. Small systems can be installed at ticket counters, bank counters, etc. You will also find loop systems in some schools and offices where there are hard of hearing people.

Here's Why Loop Systems Give Such Clear Sound

Loop systems provide wonderfully clear sound. This results in dramatically increased comprehension and increased listening pleasure. Loop systems broadcast personalized sound to both of your ears at the same time. Therefore, listening to a good loop system is like having the speaker talking right into both of your ears at the same time.

Here is why loop systems produce such clear sound:

Speech is made up of various frequencies of sound. Basically, low frequency sounds give speech its volume while high frequency sounds give speech much of its intelligence. When you hear all frequencies properly, speech is clear and easy to understand.

However, as the distance between the speaker and your ears increases, a number of things happen to degrade this clear speech.

First, as the distance increases, the volume decreases so you can't hear as well. At the same time, higher frequency sounds attenuate (get softer) with increasing distance and finally disappear altogether, leaving only lower frequency sounds. Without the high frequency sounds, speech is distorted and becomes difficult to understand. Speech is further distorted by reverberation (echoes) in rooms-especially those with high ceilings and/or hard surfaces. Finally, when there is a significant distance between you and the speaker, sounds around you mix with the speaker's voice, burying his voice in a jumble of noise.

Loop systems address all these factors. First, sounds no longer get softer the further you are from the speaker. In fact, the volume stays pretty much constant anywhere inside the loop. Second, since the speaker is speaking into a microphone held about 3 or 4 inches from his mouth, high frequency sounds are not lost in the air. Thus, it sounds like the speaker is speaking right into both your ears. Third, reverberation is cut to a minimum as the sound of the speaker's voice goes directly into the microphone rather than bouncing all around the room before reaching your ears. Finally, since the microphone is so close to the speaker's lips, little extraneous sound gets into the sound system. Thus, the end result is clear speech.

How good are loop systems? I'm no stranger to loop systems having used them for several years in different situations with good success. At a recent SHHH meeting, I decided to experiment a bit and find out. The person speaking was using two microphones. One was hooked into the room's public address system and the other was hooked into my portable loop system. Using my hearing aids' microphones, I could hear the speaker fine as far as volume was concerned. However, the clarity of his speech was poor. Distance let the high frequencies fall off and that, coupled with the reverberation and echoes in the room, made understanding him difficult. In fact, I needed to speechread him in order to get his message-and I was sitting in the front row! When I walked to the back of the room, the reverberation and noise combined with the increased distance made understanding him even more difficult.

In contrast, when I switched my hearing aids to their telecoils, I could hear everything the speaker said loud and clear. It was so clear I didn't even have to speechread. The difference was dramatic-like night and day-no matter where I stood in the room.

How Loop Systems Work

Loop systems consist of three basic parts-a microphone or other input device, a loop amplifier and a loop of wire. That's it for the transmitting side. Your own hearing aids equipped with telecoils make up the receiving side.

To set up a loop system, all you do is plug the loop amplifier into a wall socket, plug the input device or microphone into the loop amplifier, string a loop of wire around the perimeter of the room or area you want looped and connect the ends of the wire to the loop amplifier and turn it on. That's it.

Audio signals are picked up by the microphone or directly from some sound source like your TV or stereo. They are amplified by the loop amplifier and then travel through a loop of wire that surrounds the listening area. The wire loop is used instead of regular loudspeakers. 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. At this point, the loop system's job is done.

Now, it is your hearing aids' job to convert this magnetic signal into sound you can hear. When you switch your hearing aid from its microphone to its telecoil, all you are doing is connecting a small coil of wire 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 may 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, all you need to do is switch on your telecoils, 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.


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