Re: harmonic extraction (Dan Ellis )


Subject: Re: harmonic extraction
From:    Dan Ellis  <dpwe@xxxxxxxx>
Date:    Sun, 29 Mar 2009 17:47:25 -0400
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

(Jim Bashford is having problems getting the listserv to accept his messages, so I'm forwarding this on his behalf -- DAn.) ---------- Forwarded message ---------- From: James Bashford Date: Sun, Mar 29, 2009 at 5:29 PM Dear Al, I’ve listened to a number of conditions, including the odd-through-all harmonic alternation you mentioned (with 0.5 sec half-cycle and no silence between the alternating tones).  Most of my observations have used a 6-component “all-harmonic” base stimulus, because I have determined that, for me at least, the capture of individual harmonics from a complex tone (alternating with a lone sinusoid) does not readily occur for the seventh and higher harmonics.  For the six-harmonic stimulus conditions, the even-through-all and the odd-through-all stimuli behave as I reported earlier: I hear an intermittent complex tone that matches the pitch and timbre of the all-harmonic stimulus presented alone, and I hear a continuous complex tone having the pitch and timbre of the three-component stimulus (comprised of either even or odd harmonics).  These observations were made for stimuli having fundamental frequencies of 100 Hz and also 300 Hz.  So it appears that duplexity prevails when all harmonics are resolved by the auditory system.  I also listened to the original stimulus condition employing the first 10 harmonics and did hear the effect you anticipated when the fundamental frequency was 100 Hz.  Along with the continuous odd-harmonic signal having a pitch of 100 Hz, I do hear an intermittent 200 Hz having a rich timbre (one has to be careful with these judgments since it is easy to spontaneously hear out the “pure” sounding second harmonic).  Your prediction did not hold when the fundamental frequency was at 300 Hz.  At that frequency, the percept of the intermittent all-harmonic stimulus retains the pitch and timbre heard when the stimulus is presented alone. Best, Jim On Mar 27, 2009, at 6:27 PM, Al Bregman wrote: Dear Jim, Imagine your experiment in "reverse".  Alternate the all-harmonic tone with an ODD-harmonic inducer.  Then if the inducer captures the odd harmonics from the all-harmonic tone, the residual will be the set of even harmonics, and their fundamental is 2f not f.  So you ought to hear a continuous tone at frequency f, accompanied by a pulsing tone an octave higher. I am quite sure that this will occur if there is no silence between the tones.  In fact I'll turn in my badge if it doesn't come out that way. This method makes it easier to determine whether the residual harmonics are used to make their own tone, because it requires a pitch judgment rather than the more difficult timbre judgment that you reported.  If the outcome is as I expect, there will be no need to evoke an explanation in terms of duplex perception for this odd-full-odd-full stimulus pattern. But even so, this wouldn't prove that there had been no duplex perception in the example that YOU reported (even-full-even-full).  It may be that the partitioning of the spectrum is more ambiguous with your stimulus, and that this could lead to duplex perception.  It is possible that duplex perception is a top-down process that tries to make sense of an ambiguous input. Best, Al ------------------------------------------------------------------- Albert S. Bregman, Emeritus Professor Psychology Department, McGill University 1205 Docteur Penfield Avenue Montreal, QC, Canada H3A 1B1. Office:  Phone: (514) 398-6103              Fax: (514) 398-4896 -------------------------------------------------------------------


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