relative phase information in audition and vision (Timothy Justus )

Subject: relative phase information in audition and vision
From:    Timothy Justus  <tjustus(at)SOCRATES.BERKELEY.EDU>
Date:    Thu, 7 Nov 2002 19:05:46 -0800

Dear list, Here's a different question in the midst of all the high-frequency discussion. If you'll send your replies to me I'll send a single email to the list compiling them. I've been working on some studies examining possible parallels between the processing of spatial frequency and auditory frequency (e.g., Ivry and Roberston 1998) and the issue of phase information was raised to me recently; a colleague pointed out that while relative phase information seems to be unimportant when processing multiple auditory frequencies (e.g., computing pitch), it is very important in vision. If you look at an image which contains all of the same spatial frequencies at the same positions, but without being in-phase, the image is not coherent. My question is whether anyone has ideas about why this is the case. I'm starting to wonder if this results from the kind of information that phase might provide about the environment; i.e., perhaps whereas in vision phase information is important to interpreting the spatial scene correctly, this may not be as critical in audition? Does the indifference of pitch computation mechanisms to phase reflect a lack of informativity of this information about objects in the environment? Also, are other elements of audition besides pitch perception (e.g., timbre) more dependent on relative phase? I would imagine that at least for timbres dependent upon the attack like a trumpet that this would be the case. thanks for your suggestions, reference ideas, etc., Timothy Justus

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