Microphone on hearing aid. Close-up of an air con- ductor hearing aid, showing the tiny microphone (centre) and sound-conducting tube (right). This hearing aid is designed to fit on top of the ear. The transparent sound-conducting tube runs into the ear canal. Hearing aids improve hearing in people with partial deafness. Sound is picked up by a tiny microphone, amplified, and then transmitted into the ear by a tiny speaker. Each hearing aid is fine-tuned to amplify the range of frequencies most needed by the patient.