My friend Sigal pointed me to a very good (but very technical) free online book on the topic of digital sound processing (click here). It explains (in very technical terms) such things as how the human ear works, and how humans are able to tell the direction that a sound originates from (i.e. “Spatial Sound Perception“). Regarding pitch perception, it says:

So far, we have described pitch phenomena referring to the position of haircells that get excited along the basilar membrane. Indeed, the place theory of hearing is not sufficient to explain the accuracy of pitch perception and some intriguing effects such as the virtual pitch.

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