How the ear really works

Abstract

Contrary to popular belief, human eyes and ears are not general purpose light and sound analyzers; they are in fact highly optimized for detecting only very specific types of modulations on signals. Furthermore, the evolution of the visual and auditory systems was highly constrained by the fact that the receptors of both systems can only respond readily to the logarithms of the intensity of signals within various bands of frequency, and not the signal waveforms themselves. As a result, these systems cannot possibly perform Fourier analysis, wavelet analysis, linear prediction or similar types of signal processing since all of those techniques require, as inputs measurements of the signals themselves rather than just the log of the intensity of the signal. Instead, the auditory system appears to use a form of ratio detection and frequency diversity signaling in order to characterize sound modulations.<>