There are two types of acoustic feedback: that produced internally from the hearing aid - indicating a device in need of repair; and the more common external feedback produced by a leakage of amplified sound out of the ear canal and back into the microphone of the hearing aid. Feedback that occurs when the hearing aid is being inserted or removed or when your hand is cupped near the device is common and does not necessarily signal the need for action.
If you wear hearing aids, more than likely you have experienced hearing aid feedback. That annoying, alarming squeal that seems to be present at the wrong times, is sometimes an unfortunate reality of wearing the devices. However, it can be minimized or even eliminated by understanding what causes it and by learning how to make a few small adjustments. This article addresses the problem of hearing aid feedback and its solutions.
Regardless of the amount of money you spend or the type of hearing aid you buy, at sometime you will face a whistling noise while wearing them. Occasionally the sound is perfectly normal and not worthy of concern. Other times it can be a sign that something is wrong or that your hearing aid is not adjusted properly.