Full concha hearing aid. Close-up of a full concha hearing aid. This hearing aid fits inconspicuously into the middle of the outer ear (concha). The small dial controls the volume of incoming sound. Hearing aids improve hearing in people with par- tial deafness. Sound is picked up by a tiny micro- phone, 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.