The ear is the means by which the sounds of the world reach us. The external ear that is evident on humans and other creatures is only a part of the ear. The middle ear and the inner ear have different structures and contributions to the overall ability of the ear to detect sound.

The external ear consists of a hole in the side of the skull, known as the auricle or pinna, and of the ear canal. The auricle helps focus the incoming sound waves. The hole leads into the auditory canal, a roughly cylinder-shaped, small diameter canal that is about 0.98 in. (2.5 cm) long. Towards the inner end, the canal widens slightly and ends at the eardrum. The ear canal can be thought of as a shaped tube with a resonating column of air inside it, having open and...