All vertebrate species studied use peripheral frequency
analysis (selective frequency tuning) to break
down complex sounds into their frequency components.
This process tends to improve signal-to-noise ratio for
the representation and detection of some signals and
begins the process of spectral analysis that is used in
sound source localization, source segregation, and scene
analysis. Frequency selectivity has been demonstrated
in the neurophysiology and behavior of species in all
vertebrate classes that have been studied (Table 1).
Thus, frequency analysis appears to be a primitive character
among vertebrates, possibly having its origins
among some early ¢shes.