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 however, you experience feedback when you speak, chew, yawn or change position, you need to consult your audiologist. Feedback is more likely to occur in smaller hearing devices because the microphone is closer to the area at which the sound comes out into the ear. So, a behind-the-ear style may be less likely to produce feedback than in in-the-canal style device.

Usually, external feedback can be corrected by:
  • Properly reinserting the hearing aid or earmold
  • Remaking the earmold (or in-the-ear shell)
  • Plugging, or reducing the diameter of any vents (holes)
  • Reducing the amount of high frequency gain, (typically an unacceptable trade-off because of the resultant loss of high frequency hearing)
  • Altering the sound by means of filters in the hearing aids or changes in the way the devices are programmed
  • Adding a “canal lock” (a piece of plastic) to better hold canal hearing aids in place so they don’t work their way out of the ear canal as you chew
  • Recently some manufacturers have introduced digital feedback reduction. With this technology, feedback is sensed by the hearing aid and canceled by means of a new signal generated by the hearing aid itself.