Terhardt's theory and the tritone paradox (at)

Subject: Terhardt's theory and the tritone paradox
Date:    Mon, 1 Nov 1993 18:43:26 -0500

Richard Parncutt's tutorial on Terhardt's model is very instructive, but the model really explains only the basic pitch class effect--why people hear some tritone pairs as ascending and others as descending in pitch. When it comes to explaining cross-language differences, the explanation is as vague as Deutsch's. There is a difference: Deutsch (as far as I can tell from her very vague statements) appeals to variations in voice pitch, whereas Richard's interpretation of what Terhardt meant is that it relates to vowel formants and the like. What is not clear to me, however, is how the auditory system could get shaped by exposure to the multitude of speech sounds generated by vocal tracts of all sizes. The idea seems appealing, but the mechanism is quite opaque. And until this mechanism is clarified, the proposed explanation is merely a description pushed up one level (i.e., from the actual behavior to the hypothetical spectral weighting function). Richard also neglects to mention that, in my study, I found strong effects of spectral envelope for many listeners. This result is indeed atypical compared to what Deutsch and Pollack reported, and also with respect to Terhardt's model, but it is a finding in need of explanation. Apparently, spectral envelope effects do surface under certain conditions, and the Terhardt model does not allow for that. Mark Pitt (in a personal communication related to this exchange) has suggested that the effect may be related to the inability of musically untrained listeners to separate pitch and timbre--again only in certain situations. This is obviously an issue of interest to a number of people (Pitt and Crowder, Krumhansl and Iverson, Demany and Semal, Singh, Moore, etc.). However, my spectral envelope effect occurred also with musically trained listeners, I believe. (I did not interview my subjects on that point, but there were several with musical training among them.) Finally, how should the finding that I myself do not show a pitch class effect be interpreted? Do I have a flat spectral weighting function? Bruno Repp

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DAn Ellis <dpwe@ee.columbia.edu>
Electrical Engineering Dept., Columbia University