What is “feedback” and how do digital hearing aids deal with it?
Feedback is the annoying whistling sound that you may hear when you cup your hand around a hearing aid, or when the hearing aid is not seated securely in the ear. Feedback happens when the sound amplified by the hearing aid returns to the microphone and is continually reamplified. Digital hearing aids are designed to minimize this problem. For example, in one of the more sophisticated hearing aids, a “multi-directional active feedback cancellation” system monitors the sounds that go in and come out of the hearing aid to check for feedback. If feedback is identified the hearing aid will work to cancel the whistle automatically. This not only reduces the annoying feedback, but it allows the wearer to continue to receive adequate amplification – that is, the sound does not need to be reduced in order to eliminate the feedback.
