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Feedback in hearing aids

Feedback can be a problem for hearing aid wearers. It results in an annoying whistling or squeling sound.

Why feedback occurs

A hearing aid has one input: the sound comes in through the microphone. It has one output: the sound goes out of the speaker into the ear drum. But, sound moves in all directions unless something blocks it. Feedback occurs when sound coming out of the speaker travels back into the microphone and is amplified again.

Causes of the problem

There are a few things that can increase the chances of a hearing aid producing feedback:

  • The size of the hearing aid – The smaller the aid is, the closer the speaker and microphone will be – thus increasnig the chances of feedback. That is not to say that feedback will always occur in small devices – newer digital hearing aids have in-built feedback reduction that reduces or eliminates the problem.
  • The volume – The higher the aid’s volume is set, the louder the sound coming out of the speaker is. Louder sounds can travel further – increasing the chance of them feeding back into the microphone. For this reason, CIC, ITC and ITE hearing aids are not always suitable for people with moderate, severe or profound hearing loss.
  • Venting – Many hearing aids are fitted with a vent. This is a hole drilled into the shell of the aid and is a route for sound to come back from the speaker.
  • The fit – If your hearing aid does not fit perfectly tightly into your ear, it will leave gaps for feedback to travel.

What can you do to reduce feedback?

Turning the volume down is an obvious solution but you have the volume set high because you need it! If that’s not possible then seek the advice of a hearing aid professional. They will be able to reduce the size of the vent or completely close it and also check the fit of the aid. If you have had your aids for a while and they no longer fit snuggly into the ear you should be able to have new moulds made rather than buy completely new instruments. You can take a deeper look at why hearing aids whistle here.