1. Percussion waves in the air created by vibrating objects cause the tympanic membrane to vibrate.
   

2. The bones of the middle ear (malleus, incus, stapes) transmit the vibrations to the oval window on the cochlea ("snail").
   

3. The vibrations cause waves in the perilymph of the cochlea.
   

4. Hair cells on the basilar membrane send action potentials via the auditory nerve to the brain.