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Re: Auditory wheel

Hi Michael,

The "Shepard Tone" ascending sequence is inherently a loop, in the
sense that after it ascends an (apparent) octave, it is acoustically
back where it started.  If you want a more continuous stimulus,
Jean-Claude Risset has created a continuous version.

- Al Bregman

On Thu, Mar 18, 2010 at 5:22 PM, Michael H. Coen <mhcoen@xxxxxxxxxxxxx> wrote:
> Hello list,
> We are all familiar with the notion of a visual color wheel, e.g., a
> continuous, circular representation of colors in some color space such
> as HSV.  (Here's a wikipedia page with some visual examples:
> http://en.wikipedia.org/wiki/Color_wheel)
> Of course, there are many different color wheels, given that there are
> many different color spaces in which to model them.
> I'm looking for the auditory equivalent of a color wheel.  Namely, a
> parametrized, continuous method for generating a series of sounds that
> form a "perceptual loop" that has no perceived gaps.
> I've coded a several of these, e.g., a violin morphing into a piano
> morphing into a clarinet, which then morphs back into a violin.  They
> are all playing middle C and the ASDR envelopes for the generated,
> equal-length samples are identical.
> I'm doing this to measure discriminative acuity in distinguishing sounds
> along the auditory wheel, as part of a larger multimodal perceptual
> experiment.
> However, what I've found is that people with musical backgrounds have
> far greater discriminatory power in separating nearby sounds than those
> who have little training.  There are also "unintended" clues, such as
> harmonic complexity, which people appear differentially sensitive to.
> Thus, I wonder if there is any work in creating such an auditory wheel
> that might be expected to reduce bias due to background and/or culture.
>  E.g., using a heptatonic music scale may not be a good idea and sounds
> derived from familiar instruments are probably best avoided as well.  I
> would like participants to be on an equal auditory footing, so to speak.
>  I'll repeat that it is essential that there be a "loop" in the sound
> presentation that is not due to a simple repetition of sounds, e.g., a
> sine wave rising and then falling in frequency would not be useful.
> Any pointers, suggestions, code, etc., would be most welcome.
> Best,
> Michael Coen