The human ear is able to perform very useful signal processing on incoming signals. For example, there are auditory mechanisms for making sense of target signals despite noisy environments. Fine frequency and intensity differences can be measured by the ear. Von Helmholtz  proposed that the auditory nerve processes sound tonotopically; that is, by having different nerve bundles be sensitive to different frequencies. This notion of the auditory system as a sophisticated filter bank persists today and is the basis of much auditory research.
While the anatomy (i.e., the structure) of the auditory system in most animal species is fairly well understood, we still have a long way to go toward comprehending the physiology (i.e., the function of the components). There are a great many similarities among the auditory systems of many animals, including humans. Thus, in this chapter we survey the physiological knowledge garnered from animal studies. In the next chapter we survey psychophysical studies on human subjects; in succeeding chapters we use this knowledge to try to erect plausible models of how the human auditory system perceives the pitch of speech and music and how it perceives speech.
14.2 ANATOMICAL PATHWAYS FROM THE EAR TO THE PERCEPTION OF SOUND
The neocortex is that large part of the human brain that ultimately determines the ...