[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: perceptual segregation of sound


If you think about what the auditory system is supposed to do, one of the fundamental tasks is to determine the nature, number and location of sources in the environment. This fundamental task is accomplished quite handily by much "less intelligent" organisms than ourselves, so I think one should avoid the temptation of ascribing too much to "top down" processing. Although it is hard to say where auditory objects (to use a controversial term) are formed (if indeed they are formed at any one place), certainly at the more peripheral levels of auditory processing there are mechanisms for grouping frequencies that are correlated, which may be automatic, as in Bregman's preattentive stage. The effects of auditory attention also seem to implemented at the cochlear level, even though it generally considered a more top down process. So it is not as clear cut as conventional models would have it. If you want to appeal to introspection, don't use hypothetical cases that may never occur (such as hearing two lions roaring simultaneously) but do a little listening in your everyday environment and ask yourself if the imemdiate impression is of one mass of sound that eventually resolves itself into individual components or of separate sources. Obviously, this is dependent on the how different the sourses are acoustically, how offset they are in time, and how spatially separated they are, and top down processes are useful for resolving ambiguous cases.

In any case, I would strongly recommended you look at the archives of the Auditory list for our previous discussion on this topic, which was quite interesting.

Brian Gygi