Hearing aid squealing or hearing aid whistling is technically known as Hearing Aid Feedback or Acoustic feedback. The hearing aids elevate the sound picked up by the microphone; this sound reaches the ear canal. If this sound leaks out of the ear, it may be picked up by the same microphone and amplified again which is referred to as hearing aid feedback. In the latest digital hearing aids, this feature involves the automatic suppression or reduction in the sound when the hearing aid detects the feedback.