Re: Auditory objects (Stephen McAdams )

Subject: Re: Auditory objects
From:    Stephen McAdams  <Steve.McAdams(at)IRCAM.FR>
Date:    Tue, 16 Apr 1996 10:39:38 +0200

bert(at)EPX.CIS.UMN.EDU wrote: > > I am making a demo for my Hearing Science course on > auditory object perception. I would like to create a > demo that I heard S. McAdams present during his talk at > berkeley a few years ago, but I don't know the details > of the signals. > This demo was created by Roger Reynolds and Thierry Lancino at IRCAM on the basis of work I was doing on FM in the early 80s. It was taken from a piece called Archipelago by Reynolds. It was created in the following way: Take an oboe sound. Analyze it with a phase vocoder technique which gives as output the functions of amplitude and frequency change over time for each harmonic. Then resynthesize the sound with additive synthesis, applying modifications to these functions. The modifications applied by Reynolds was first of all to stretch the 2 sec original sound out to about 30 seconds, by simply reading through the amp and freq control functions more slowly (note that with additive synthesis this will not affect the original pitch though one needs to take care in the region of the attack). Even and odd harmonics were sent to separate channels so that they could be individually spatialized (in my demo version they simply come from separate speakers). Then after the beginning of the sound during which the oboe percept is heard slowly increase the modulation width of a frequency modulation applied to odd partials, fade this modulation down and then do the same to the even partials, then fade back in the modulation on the odd partials but at a different modulation rate than that applied to the even set. The odd and even partials segregate into separate auditory images. The odd partials give the original pitch and a hollow, clarinet-like timbre. The even partials give a pitch an octave higher (surprise!) and due to the formant-like spectrum of the oboe a soprano-like timbre. Curiously this sopranoness depends on the presence of the vibrato. Voila, amusez-vous bien! Steve

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