The sing-song of old man human ear

Otoacoustic emissions evoked from the inner ear are the barely audible, signature by-product of the delicate hydromechanical amplifier that evolved within its bony walls. Compared to the sounds evoked from the ears of common laboratory animals, otoacoustic emissions (OAEs) from human ears have exceptionally long delays, typically exceeding those of cats, guinea pigs, and chinchillas by a factor of two to three. This presentation asks “Why are human OAE delays so long?” and reviews efforts to find answers in the mechanical frequency selectivity of the inner ear. The road to understanding species differences in OAE delay has led to the identification of new invariances and the emergence of new questions.