Re: Computational ASA -- how many sources can humans perceive?

[Valeriy Shafiro <Valeriy_Shafiro@xxxxxxxx>]

From: "Maher, Rob" rmaher@ECE.MONTANA.EDU

>It is sometimes argued that "humans can do separation, so the problem must
>be soluble."  I would argue that humans do source _identification and
>tracking_ very effectively, but perhaps humans do not actually solve the
>computational _separation_ problem, in the sense that the individual
vectors
>'B', 'C', etc. are extracted in a neural signal processing context.

I would like to ask a further question: Do we, in fact, know how many
independent sound sources in a mixture humans can perceive?  Thus far I
know of only one research report where human listeners were asked to
identify sound sources in a recorded "real-world" sound mixture (Ellis, D.
P. (1996). Prediction-driven computational auditory scene analysis).  We
have been talking about this issue with Brian Gygi, and from the few
related reports that Brian found, it appears that humans may not be that
good in simultaneous perceiving independent sound sources.  For instance,
Jennifer Tufts and Tom Frank J. Acoust. Soc. Am. 101 , 3107 (1997) found
that the accuracy of judging the number of talkers in a multitalker mixture
drops considerably when there are more than 3 talkers.  There is also a
report by David Huron (Music Perception, Vol. 19, No. 1 (2001) pp. 1-64.,
or on-line
http://www.music-cog.ohio-state.edu/Huron/Publications/huron.voice.leading.html
 ) that estimating the number of musical lines in
 polyphonic music worsens considerably after 3.  Some anecdotal evidence
for this limit also comes from movie sound effect designers.  This is a
citation from Walter Murch, a renown sound effect artist: "There is a rule
of thumb I use which is never to give the audience more than two-and-a-half
things to think about aurally at any one moment. Now, those moments can
shift very quickly, but if you take a five-second section of sound and feed
the audience more than two-and-a-half conceptual lines at the same time,
they can't really separate them out. There's just no way to do it, and
everything becomes self-canceling." (cited from
http://www.filmsound.org/murch/waltermurch.htm)

Any thoughts, comments, and references relevant to this issue are
appreciated.



-------------------------------------------------------------
Valeriy Shafiro
Communication Disorders and Sciences
Rush University Medical Center
Chicago, IL

office (312) 942 - 3298
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