A whistling hearing aid can be very embarrassing. The whistling sound is called acoustic feedback and can often be quite a challenge for the audiologist with some older hearing aids. Most patient’s can hear their own hearing aids whistle. When they hear the aid whistling, they usually turn the volume down to get rid of the feedback. The problem with that is that they then can’t hear as well because the volume has been reduced. Unfortunately, if the patient’s hearing loss is very severe, the patient may be unaware of the whistling. However, other individuals near them may hear it and find it very annoying. Have you ever been in public and heard that sound?
There are two types of feedback. The first type is called external feedback. External feedback may occur if the ear mold fits loosely and allows the amplified sound exiting the tip of the hearing aid to leak out of the ear canal and find its way back to the microphone. The feedback is similar to what you hear at a concert. The intense music from the loudspeakers is picked up by the microphone on stage and you hear a loud annoying squeal. If someone experiences feedback with their hearing aid, the ear mold should either be adjusted or remade to reduce the leakage of amplified sound. Excessive earwax blocking the ear canal can increase the chances of external feedback. Instead of the sound reaching the eardrum, the sound bounces back out of the ear to the hearing aid microphone.
The second type of feedback is called internal feedback. Internal feedback may occur if the microphone or the receiver of the hearing aid is touching another component in the aid. In this case the internal components need to be adjusted or re-positioned so they are not touching any surface.
The good news is that many new hearing aids come with software to cancel the annoying feedback. This newer feedback cancelling technology allows us to give the patient the adequate gain they need without the feedback.