Subject: Re: granular synthesis and auditory segmentation From: Peter Cariani <peter(at)epl.meei.harvard.edu> Date: Mon, 19 Oct 1998 17:37:03 +0100R. Fabbri wrote: > >I'd love to hear about *psychophysical* auditory perception > >experiments that unambiguously demonstrate temporal > >processing in humans in the 3 to 5 kHz range! My expectation > >is that such results have not been found... Few psychophysical experiments unambiguously demonstrate that a particular neural mechanism is used, because there are many possible neural mechanisms that can carry out the same function. What they sometimes do, however, is show that sole reliance on a given kind of neural information is not sufficient to account for perceptual capability (which rules out that coding scheme) or that psychophysical judgements covary with the availability of particular kinds of neural information (which suggests but does not prove that that particular information is used). >From 3kHz to 5 kHz the quality of timing information as well as tonality and frequency discrimination decline precipitously. At 3kHz there is considerable phase-locking; at 5 kHz it is much much weaker. 1. Phase locking and musical tonality covary. -- one can still make good octave judgments if the upper tone is at 3 kHz, but this becomes guesswork by the time one gets up to 5 kHz. When I made a melody of pure tones whose upper tones descended systematically from 10 kHz downwards, for me the melody became easily recognizable only when the upper tone had a frequency below 4 kHz. 2. Phase locking and frequency discriminations covary. Models of frequency discrimination (Goldstein & Srulowicz first-order interval model) that use phase-locked information predict relative frequency jnd's as a function of frequency in the 3-5 kHz range. If one extrapolates the decline of phase-locking out to 10 kHz, these models predict well the relative frequency jnd's out to 10 kHz. There are caveats and complexities in the interpretation, but in general human and cat jnd's decline with frequency in a manner that is generally consistent with the decline of phase locking, whereas rate place information shows the opposite trend, getting relatively better as frequency increases. But why should the burden of proof be placed on just one putative coding scheme? What in your opinion is the unambiguous evidence in favor of some other (name your favorite) coding scheme in the 3-5 kHz range? Peter Cariani McGill is running a new version of LISTSERV (1.8d on Windows NT). Information is available on the WEB at http://www.mcgill.ca/cc/listserv