Obviously, if the transmitter is sending light waves, the receiver must be able to pick up light waves. You cannot use an infrared transmitter with an FM receiver. While the transmitter and receiver must communicate in the same language, coupling devices, for the most part speak the same language. Couplers are separate from the receiver/transmitter system. If it weren’t for a lack of uniformity in connecter plugs, couplers would, for the most part, be interchangeable among the different ALDs.
The coupling device is the mechanism that takes the transmitted signal from the receiver to the ear. How does that work? The receiver converts the signal to electromagnetic energy. The electromagnetic energy still must be converted into something we can hear-sound waves. The next step will depend on whether the individual is wearing hearing aids or not, and if their hearing aids have a T-coil. T-coils are discussed in more detail in the next slide.
If the individual does not wear hearing aids or does not have T-coils in their hearing aids, they would use headphones (top) or earbuds or earphones (the middle 2 pictures). This is just like plugging headphones into a radio. The signal is converted to electromagnetic energy and transmitted to the speakers in the headphones, where it is converted into acoustic output-sound waves.
But what about this mysterious T-coil? Well, if the individual is wearing a hearing aid with a T-coil, they flip the switch from ‘mic’ to ‘T’. Then, the signal is still converted to an electromagnetic signal in the receiver, but the coupler is one that sends the signal directly to the T-coil of the hearing aid (the bottom 2 pictures). The hearing aid then converts the electromagnetic signal into sound waves and sends the waves into the individual’s ear canal. Why is this better? Because the sound is not being converted to acoustic waves until it reaches the individual’s ear canal. This helps to prevent any degradation of the sound and delivers the best quality sound possible to the individual. These devices are available for one or both ears, and include neckloops (bottom left) and silhouettes that fit directly behind the hearing aid (bottom right).
You should be aware that there are other methods that are not covered here. The picture on the far left is an example of direct audio input, where the receiver plugs directly into the hearing aid, thus eliminating the coupling device.
Noisy situations are equally difficult for cochlear implant users, who may also receive great benefit from ALDs. Some implants do not have a volume control, only a sensitivity knob. The effect is like turning up the volume on a hearing aid…all the room noise is turned up with it. CI users will need an ALD with a jack, and a patch cord to connect it to the implant.
