The whistling or feedback heard when coming in close contact with the hearing aid is a normal phenomenon. It is a result of some of the amplified sound of the hearing aid leaking out from around the hearing aid mould that sits in the opening of the ear canal or the soft domes that are worn within the ear canal. This “leaked”
amplified sound then bounces back into the hearing aid, especially when it is in contact with a nearby surface, in this case your face. There are a number of reasons why hearing aids can be prone to whistling.
- If there is excess wax in the ear canal the amplified sound directed into the ear canal “hits” the wax and then bounces around the ear mould and into the hearing aid’s microphone. So, it may be worth having the ear's cleaned by a doctor.
- If the fit of the hearing aid or the hearing aid mould is too loose, the amplified sound leaks out and bounces back into the microphone – often a new, better fitting mould can solve this problem. In some cases a longer mould is the solution and in others a shorter mould can be better. A temporary solution is the use of a non-allergenic gel such as Auragel that coats the hearing aid mould or hearing aid shell and can help reduce the whistling by reducing the amount of sound that can leak between the hearing aid and the skin of the ear canal. Do not apply the gel to the sound bore or mould opening where the sound is emitted, as this could damage the hearing aid, as well as block the sound.
- Although highly unlikely if the hearing aid has been fitted by an audiologist, whistling will occur if the hearing aid is over-amplified in the higher frequencies, so it is worth mentioning the problem to your audiologist/audiometrist.
Also, if your friend has a severe or profound hearing loss, it can be very difficult to stop this whistling completely because she will require significant amplification and, often no matter how good the hearing aid feedback cancellation system is, there will be a greater chance that sound will escape back into the microphone. In general, the newer hearing aids available now have better feedback cancellation systems, so whistling is less of a problem than it used to be.