Design objectives

Virtually all environmental and biologically significant sounds change their amplitude, frequency, and phase, from instant to instant. The ear must be capable of analyzing the time-varying features of these sounds and representing them in a spatiotemporal array of neural discharges in the fibers of the auditory nerve. When analyzing a signal, its frequency spectrum and temporal characteristics are reciprocally related. The spectrally simplest signal, a continuous sine wave, corresponding to a pure tone in acoustics, has only one spectral component, the frequency of the sound, and lasts forever. In contrast, the temporally simplest signal, an impulse, corresponding to a click in acoustics, is infinitesimally short in duration but contains all frequencies. Natural sounds present a continuum between these