Final answer:
The two most common causes of whistling and squealing in a hearing aid are feedback and poor fitting.
Step-by-step explanation:
The two most common causes of whistling and squealing in a hearing aid are feedback and poor fitting.
Feedback occurs when sound that is amplified by the hearing aid goes back into the microphone and is re-amplified, creating a loop. This loop can cause a high-pitched whistle or squeal.
Poor fitting of the hearing aid can also cause whistling and squealing. If the hearing aid does not fit properly in the ear, sound can leak out and be picked up by the microphone, resulting in feedback and the whistling or squealing sound.