within- vs. across-stream organization (Greg Sandell )

Subject: within- vs. across-stream organization
From:    Greg Sandell  <sandell(at)EPUNIX.SUSSEX.AC.UK>
Date:    Fri, 14 May 1993 10:07:56 -0400

Pierre, Bill and Punita, Thanks for your suggestions in response to my posting. However, all the works cited (musical or experimental) seem to be concerned with differences between voices that enhance streaming (e.g. one voice being soft and the other loud, one voice being of timbre A and the other of timbre B). This fundamental aspect of stream segregation was not what I was asking about (although I was glad to have been nudged towards Hartmann & Johnson, and enjoyed looking over the pieces mentioned by Pierre). The case where one voice has timbre A and the other timbre B enhances streaming by highlighting differences *across* the voices. This indeed is one form of "organization." However, I am interested in forms of organization *within* the individual voices that enhance their ability to stream. Perhaps the best way to clarify the question (which I sense it needs) is by another example. Say I have two alternating human voices singing a list of random numbers on a single pitch, and the voices are the same person (your terminal will need a non-proportionally-spaced font to read this): voice 1: 5 1 8 2 3 6 7 9 1 4 0 voice 2: 6 2 1 8 2 2 6 3 5 3 (time ------------------------------------------> ) There will be nothing differentiating the voices, so only a single stream will form. We can cause streaming to occur, however, if we differentiate the voices in some way. We could put them at different pitch levels; we could make them different persons; we could have one voice reading odd numbers and the other voice reading even numbers (although I'm not sure that would be enough). That would be an across stream organization. But consider the following within-stream organization. Suppose voice 1 sings short sequences of numbers that ascend, while voice 2 sings short sequences of numbers that descend, as shown below. This would be a within-stream organization. voice 1: 5 6 7 2 3 4 5 4 5 6 7 voice 2: 6 5 4 3 9 8 7 3 2 1 Will this form streams? Maybe not on the basis of that difference alone. But will it *enhance* stream formation? For example, if it had been found that a 200 Hz separation between the voices in the first case was the minimum distance at which streams would form, will this within-stream organization reduce that required distance to, say, 150 Hz? And of course, is there any research which looks into this kind of thing? I hope this example makes it more clear; thank you for your patience! -- Gregory J. Sandell (sandell(at)epunix.sussex.ac.uk) Lab. of Experimental Psychology, University of Sussex Brighton BN1 9QG England +44-273-678058

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