Re: Granular synthesis and auditory segmentation ("Richard J. Fabbri" )

Subject: Re: Granular synthesis and auditory segmentation
From:    "Richard J. Fabbri"  <fabbri(at)NETAXIS.COM>
Date:    Thu, 15 Oct 1998 17:30:34 -0400

Peter, >[I say "roughly reflect", because half-wave rectification >does subtly alter the form of interspike interval >distributions and autocorrelation functions. >The autocorrelation of a sinusoidal component has the >form of a cosine of the same frequency; the autocorrelation >of a half-wave rectified component has flattened troughs, >but closely resembles that of the unrectified component >near the peaks. The positions of peaks and troughs are >unchanged by half-wave rectification. When you listen to >a half-wave rectified pure tone, it does sound very >slightly different in timbre, slightly buzzy, but the >pitch is the same,so the pure tone and its rectified >counterpart don't sound all that different. I think >Didier is right, however, in insisting on factoring >in the effects of cochlear filtering first -- there >are simple thought experiments with waveforms having >positive-negative asymmetries which nevertheless still >sound the same when polarities are reversed. If we >only listened to the positive parts of asymmetric >waveforms, different polarities should sound different.] ... Didier's example of listening to a Halfwave Sine vs a Sine is not equivalent to the transduction function provided by the neural HALFwave action caused by a neural refractory period when the acoustic waveform is of the opposite polarity. ... Basically, the Basilar/Tectonic membranes are mechanically driven by the BIPOLAR Sine waveform which is THEN HALFwave transduced WHILE the Inner Hair Cells undergo the FULLwave mechanical motion of a FULLwave sinewave. ... This is NOT the same thing as providing a HALFwave ACOUSTIC waveform as THAT sets-up a QUITE different quiescent base-line (+/-) reference for the Basilar Membrane than does a SINE wave. ... i.e., the EFFECT is HALFwave transduction into neural pulse rates while the transduced mechanical MOTION is FULLwave. Regards, Rich Fabbri McGill is running a new version of LISTSERV (1.8d on Windows NT). Information is available on the WEB at

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