Hearing test. View of a patient undergoing a hearing test after a cochlear implant. The hands of a technician are placing a sound emitting device into the patient's ear. The technician is using the device to produce sounds of varying pitch and loudness in one ear at a time. The sounds decrease in volume until they become inaudible. A patient will respond each time they detect a sound by pressing a button. Cochlear implants are used to treat severe deafness. They are tiny devices which relay signals from a microphone directly to the nerves of the ear. They enable the user to hear speech patterns and aid the understanding of lip reading.