Re: spatial separation and ASA (Al Bregman )

Subject: Re: spatial separation and ASA
From:    Al Bregman  <bregman(at)HEBB.PSYCH.MCGILL.CA>
Date:    Wed, 31 Jan 2001 21:00:27 -0500

Dear List, In reply to Pierre Divenyi and others, perhaps we should not be quite so pessimistic about the role of spatial separation in allowing signals to be segregated. It is true that laboratory studies such as Pierre's have shown that when fairly steady signals have to be segregated by place alone, performance is not very good. But in a natural environment, it would be unlikely that sounds at different locations would be so similar or so steady. The role of spatial cues in segregation may be to enhance the segregation based on other factors. In other words, in cases where two signals were partially segregated by factor X, adding a difference in location would strengthen the segregation. A good example might be where X stands for independent patterns of amplitude fluctuation. These fluctuations would provide instants at which better independent spatial estimates could be made. Stringing similar spatial estimates together sequentially, along with the spectrum of the signal at those instants might give a clearer picture of the two sounds. (We know that spatial differences do play an important role in SEQUENTIAL grouping.). A similar argument could be made for cases in for other The idea that spatial information does make a substantial contribution to segregation -- under conditions where the sounds also differ in respects other than spatial -- may explain why stereophonic recordings allow a clearer perception of the individual instruments (or groups of instruments) than monophonic recordings do. My point about spatial information was not that it was very weak but that it was only one of a number of cues for sound separation. To this should be added the idea that it may need those other cues in order to be effective itself. Al

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