High Quality Content by WIKIPEDIA articles! A hearing aid is an electroacoustic device which typically fits in or behind the wearer`s ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and direct it into the ear canal. Similar devices include the bone anchored hearing aid, and cochlear implant.