by Neil Bauman, Ph.D.
Several people have commented on the orientation of the t-coils (telecoils) in their hearing aids and cochlear implants and it’s impact on whether they hear well in looped rooms or not.
For the best transfer of signal from a room loop to the t-coils in your hearing aids, both the room loop and your t-coils have to be oriented in the same plane. Thus correct orientation is very important. For room loops, you want your t-coils oriented vertically.
Unfortunately, for telephone use, you want your t-coils oriented horizontally. Thus these two orientations are just plain incompatible.
Depending on their perceived use, some manufacturers orient their t-coils vertically, some horizontally and some split the difference and mount their t-coils at 45 degrees.
If you want to listen to room loops and have a hearing aid or cochlear implant (Nucleus 5) that has its t-coils mounted in the horizontal plane, you are in trouble unless you learn the secret of exactly where to sit in a looped room.
In one of my presentations, I demonstrate that no matter what your t-coil orientation is, there is a “sweet spot” somewhere in the loop that will be just right for your specific t-coil orientation.
Here’s how to find that “sweet spot” for your particular hearing aids. Note: the following applies to a simple perimeter room loop mounted on the floor.
Briefly, if your t-coils are oriented vertically, then you can sit anywhere inside the looped area as long as you stay a foot or more inside the loop wire.
If your t-coils are oriented horizontally, then you won’t hear well (or at all) inside the looped area. Rather, you need to sit precisely on top of the loop wire (exactly where you’d be in the null if you had vertically-oriented t-coils). That is your “sweet spot”. However, not all spots along the loop perimeter will work for you. This is because although your t-coils are oriented horizontally, they are still aimed in some specific direction horizontally and this could be any one of 360 degrees. To make it work the best, your t-coil has to be oriented at right angles to the room loop wire at the place where you are sitting.
Thus if your t-coil is mounted transversely in your hearing aids (that is, aligned with a line going through your head from ear to ear), then you need to sit on a side of the looped room. However, if your t-coils are oriented horizontally with their axis in the same plane as a line going from the back of your head to the front, then you need to sit on top of the loop wire at either the back or the front of the room loop.
If your t-coils are oriented horizontally and you don’t know which direction they “point”, just move around on the loop wire. If you sit over the wire on one side of the room or the other and find you can’t hear unless you turn your head 90 degrees and face the wall instead of the front, then you know your t-coils are mounted “front to back” and you need to move either to the front or back of the room loop. In like manner, if you are sitting over the front or back wire and need to turn your head 90 degrees in order to hear, then your t-coils are mounted transversely and you need to move and sit over the left or right side loop wire in order to hear.
If your t-coils are mounted at 45 degrees, then typically you can sit anywhere and still hear, but theoretically, you’ll hear the best if you are close to the loop wire, but not right over it. Since t-coils set at a 45 degree angle have both a vertical and a horizontal component, if you are sitting near the right side of the loop and don’t have a good signal, try turning your head sideways. If that improves the signal, then you need to move either to near the front or the back of the loop wire (and vice versa).
The above assumes that you are sitting in a simple perimeter loop (or figure of eight loop). If the loop is a fancy phased array, then you can basically sit anywhere and hear well no matter how your t-coil is oriented. However, phased arrays are typically only used in large venues that have been professionally installed. Home loops and loops used in small meetings (such as HLAA meetings) are typically simple perimeter room loops. That is why correct t-coil orientation or where you sit makes a decided difference. Now you know the secret.