Institut für Klinische Physiologie / Inst. of Clinical Physiology

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Alfred H. Gitter
Brief history of hearing research

Ancient times

The law of Pythagoras, the first law in the field of hearing, states that the doubling of sound frequency leads to an octave sensation. In the fifth century B.C., Empedocles compared the funnel-like outer ear with a bell and claimed that it is capable, not only of receiving, but also of generating sound. Aristotle' s theory of an air-filled cavity in the head that acts like a resonator dominated concepts of hearing physiology for 2000 years [Gitter, 1990a].

The anatomists of the 16^th century described the middle-ear cavity with the 3 ossicles and the bony labyrinth including the cochlea. Willis speculated in 1672 that different "tones" (species audibilis) may excite different fibers of the eighth cranial nerve. In 1683, DuVerney and Mariotte derived the principle of tonotopical representation of tones along the cochlea. However, Aristotle's aer implantatus was contradicted by Cotugno as late as 1760 [Gitter, 1990b].

In 1851, Corti described the structure of the sensory epithelium in the cochlea and detected the outer hair cells [Gitter and Preyer, 1991]. Helmholtz corrected the theory of DuVerney and Mariotte in 1863 on the basis of Hensen's precise microscopic description of the cochlea and Ohm's law of the applicability of Fourier analysis to sound. Psychophysics was systematically developed by physicists like Mayer, Lord Rayleigh, Savart, Seebeck and others. In 1870, Töpler and Boltzmann were the first to have estimated the sensitivity of hearing [Gitter and Preyer, 1992].

In the second quarter of the 20^th century, experiments by the Nobel prize-winner G. von Békésy led him to the concept of the travelling wave, a modification of Helmholtz's theory. In the last quarter of the 20^th century, research focuses on active processes, which amplify and tune the travelling wave in the cochlea. Lateral inhibition, as in vision, seems to be absent in hearing. Otoacoustic emissions, i.e. sound that is produced in the cochlea, provide direct evidence for this new view of hearing physiology, as was shown by Kemp in 1978 [Gitter and Preyer, 1992]. However, Empedocles raised the issue 2500 years before [Gitter, 1990a].