How We Hear

The funnel shaped outer ear functions to collect sound waves which are then transferred through the ear canal to the eardrum.

Sound waves cause the eardrum to vibrate. This vibration stimulates the movement of the middle ear bones, which are attached to the eardrum on the middle ear side. These bones amplify the vibrations received by the eardrum and transmit them to the oval window, a small membrane on the cochlea, which separates the middle ear from the inner ear.

On the cochlear side of the oval window is fluid (or lymph) which fills the cochlea. Vibration of the oval window causes pressure waves within the cochlear fluid. The pressure waves stimulate movement of thousands of acoustic hair cells in the cochlea, converting the sound signal into electrical stimuli via neurons. These electric stimuli are transmitted to the brain via the eighth cranial nerve, or auditory nerve. In the brain these stimuli are processed and are perceived as sound.