Hearing aid interference can be caused by a variety of factors, including electromagnetic interference from sources such as cell phones, televisions, and computers, as well as RF interference from wireless devices like Bluetooth and Wi-Fi.
Other potential sources of interference include electronic devices worn near the hearing aids, such as pacemakers, and the presence of certain types of metal, such as aluminium or steel. Additionally, feedback can occur when the microphone on a hearing aid picks up the amplified sound coming out of the speaker, which can cause a whistling sound.