Features

A hearing aid has a microphone, amplifier and receiver. Sound enters the microphone and is converted to electrical impulses. The amplifier strengthens those impulses and the receiver translates them back to louder sounds.

Function

Acoustic feedback occurs when the sound that leaves the receiver is diverted back through the microphone to be amplified a second time. At that point, the sound becomes a whistle.

Effect

According to Preferred Hearing Solutions, high-frequency sounds have a shorter wavelength than lower-frequency sounds, so they're more likely to escape from the ear and come back through the microphone.

Considerations

Many individuals with hearing impairments have lost the ability to hear high-frequency sounds, so they may not hear the whistling sounds of acoustic feedback that are audible to those around them.

Tips

Preferred Hearing Solutions shares some tips to reduce acoustic feedback. An audiologist can evaluate the fit and function of your hearing aid, change the distance between the microphone and amplifier, or modify the way your aid amplifies high-frequency sounds. In some cases, the solution may be as simple as removing excess earwax.

Source:

Preferred Hearing Solutions: What is Acoustic Feedback?

Palo Alto Medical Foundation: Hearing Aids

More Information:

Listen Up: Hearing Aid Feedback