This book describes the major steps by which the mammalian ear transforms sound into nerve impulses. The author leads us along the pathway followed by an acoustic signal--collected by the outer ear, augmented by the middle ear, then delivered to the inner ear where the minuscule vibrations of the sound waves are transformed into nerve impulses. At each stage, the basic mechanisms are described qualitatively in terms of current theories and illustrated with experimental data. Where appropriate, related mechanisms in the ears of other vertebrates are considered. It is shown that the mammalian ear does an exquisite job of translating sound signals into a very robust nerve-pulse code. The book concludes with descriptions of some common ear impairments and a brief survey of the treatments available for them. The text is integrated with animations of mechanical and neural phenomena available through the Internet.