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Helmholtz and combination tones

As demonstrated by the thread on Helmholtz and combination tones, it is pretty amazing that Helmholtz came up with equations describing the production of combination tones although he apparently did not or could not specify their structural and physiological bases.  There is an interesting indication of how this polymath’s mind worked with limited information that is indicated by a basic error he made in the first edition of his Sensation of Tones (1863).  He initially attributed the frequency analysis occurring in the inner ear to tuned properties of the rods of Corti that are adjacent to auditory nerve fibers on the basilar membrane.  He abandoned this theory in later editions when it was shown that amphibia and birds lacked these structures.  He then attributed the frequency analysis to stretched and loaded nerve fibers on the basilar membrane.  However, his initial proposal concerning the rods of Corti is eerily similar to the currently accepted role of bundles of stereocilia as an initial stage in frequency analysis.

Richard M. Warren
Research Professor 
  and Distinguished Professor Emeritus
Department of Psychology
University of Wisconsin-Milwaukee
PO Box 413
Milwaukee, WI  53201
(414) 229-5328