A patient's eardrum is badly damaged and no longer vibrates properly. The patient's ossicles, cochlea and auditory nerve are healthy. A surgeon fits a small device that picks up sound and makes the ossicles vibrate at the same frequency as the sound. The patient can now hear.
Which explains how the device allows the patient to hear?
The ossicles pass the vibration to the oval window, making pressure waves in the cochlear fluid that bend hair cells.
The ossicles make the air in the ear canal vibrate, and this air carries the sound into the cochlea.
The ossicles pass the vibration straight into the auditory nerve, which carries the vibration to the brain.
The ossicles change the vibration into electrical impulses, which then bend the hair cells in the cochlea.