From: malcolm@interval.com (Malcolm Slaney)
Date: Fri, 2 Sep 1994 10:58:56 -0800
Subject: Distance Perception at CCRMA
Message-Id: <9409021758.AA00267@interval.interval.com>

Now that we've heard many things about sound separation, it's time for
something different.

The next CCRMA Hearing Seminar will be lead by Jan Chomyszyn.  He will be
talking about his work on distance and reverberation perception.  What cues
are important to our auditory system when we judge the distance to a sound
source?  Does the amount of reverberation (due to room size) cause our
loudness percept to change?

Jan will be talking about work he has been doing at CCRMA for the last
couple of years.  He'll be taking his work to ICMC later this month.

        Who:    Jan Chomyszyn (CCRMA)
        What:   Distance and Reverberation Perception
        When:   Thursday September 8 at 10:30 AM
        Where:  CCRMA Library (Top Floor of the Knoll)

See you all at CCRMA.

-- Malcolm
P.S.  Just a reminder... I am not scheduling seminars for the weeks of 9/15
and 9/22.  Let me know if you know of somebody coming through town who
should talk.


Date: Wed, 31 Aug 94 20:27:33 -0700
From: jan@ccrma.Stanford.EDU


Many factors contribute to the impression of space and the location of
sound sources, including appropriate reverberation, and balance of loudness
and timbres of the sounds used in the composition. Some of the parameters,
which provide cues to distance of the sound sources are correlated in a
natural reverberant environment. A typical example is direct-to-reverberant
sound energy ratio and intensity, which change reciprocally along the
physical distance between the sound source and the listener.

        However, the percepts arising from the physical cues do not always
follow the same relationship. Since the beginning of this century
researchers are aware that changes in loudness and changes in distance may
sometimes form equivalent concepts for the listeners [Gamble, 1909]. As a
part of his "physical correlate theory" Warren [1973] noticed that loudness
judgements of his stimuli (speech) depended on the degree of reverberation.
Recently Chowning [1990] observed that loudness constancy might take place
in room environment in an analogous way to the size constancy in vision. In
visual perspective, to preserve the impression of size constancy of an
object, the physical size of the object has in fact to be diminished in
proportion to the provided perspective.  Is this also the case in auditory
perspective?


        Imagine sounds in a room varying as to the effort induced by the
player and, proportionally, the amount of reverberation, which invoke the
sensation of distance, and  auditory perspective. In such conditions, if
"size constancy"   appears in the auditory world, the loudness of the sound
source will be perceived rather than the loudness of the sound wave at the
listeners' ears in a loudness judgement of such sounds. For the two sounds
of equal intensity (and the same, or similar timbre), the sound played with
a greater effort and carrying a higher amount of reverberation would be
perceived as louder. According to the hypothesis, for the listeners these
cues should suggest that the sound was played from a greater distance,
hence it must have been louder at the source.




[Chowning, 1990] John Chowning. Music form Machines: Perceptual Fusion &
Auditory Perspective - for Ligeti. Report No. STAN-M-64, CCRMA Department
of Music,  Stanford University, pp. 7-14, 1990,

[Gamble, 1909] E. Gamble.  Minor studies from the psychological laboratory of
Wellesley College, I. Intensity as a criterion in estimating the distance of
sounds. Psychological Review, 16, pp. 416-426, 1909

[Warren, 1973] R.M.Warren.  Anomalous loudness function of speech. Journal of
the Acoustical Society of America, 54, pp. 390-396, 1973