Some of the men suffered burst eardrums. At least one man was struck unconscious from the force of a cannon ball against the iron. The men quickly learned to stay away from the walls.
The outer ear picks up sound waves from the air around it and moves them along your ear canal to the middle ear, where the sound waves vibrate the eardrum, sending the sound along to the inner ear.
In the ear, it innervates the stapedius muscle which dampens the vibration of the stapes, a small bone that help transmit vibrations from the eardrum; this protects you from loud noises.