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Re: Mike and Brad on Acoustic Flow Field Generation

Dear list,

I recently have been suffering with a blocked right ear and have
acquired some down-to-earth experience with spatial perception.
In addition to noticing that all sounds seem to come from the
side of my good ear, I have also experienced great difficulty in
hearing sounds in reverberant environments (like Mike's hallway).
Apparently auditory scene analysis (ASA) depends strongly on
spatial cues for segregating the direct signal from
reverberation.  Possibly the typical recording of a loudspeaker
does not adequately capture the spatial information (i.e., the
spatial properties of the loudspeaker signal versus those of the
reflections in the room) which would permit ASA to work

This statement would imply that if the recording were done in
stereo through an artificial head equipped with artificial
pinnae, and played back over headphones that by-passed the pinnae
of the listener, he or she would hear the loudspeaker as well
from the recording as from being there in person.

Albert S. Bregman, Emeritus Professor
Dept of Psychology, McGill University
1205 Docteur Penfield Avenue
Montreal, QC, Canada H3A 1B1

     Phone:  +1 (514) 398-6103
     Fax: +1 (514) 398-4896
Home phone & Fax: +1 (514) 484-2592
Email:   al.bregman@mcgill.ca

----- Original Message -----
From: Bradley Wood Libbey <gt1556a@PRISM.GATECH.EDU>
Sent: 30-Aug-01 8:57 AM
Subject: Re: Acoustic Flow Field Generation

> Mike,
> I have also noted degraded recordings from loudspeakers in
> environments.  When I record speech from a loudspeaker and then
play this
> recording back to a listener on headphones I find it to be less
> intelligible than a person simply listening to the loudspeaker
in the same
> environment. Even though I took considerable pains to calibrate
> balance the recording and playback equipment.
> Unfortunately I don't have a direct answer, but in my case I
suspect it is
> related to imperfect recordings interacting with the acoustic
> For example the interaction of reverberation, noise, and the
> directionality of the ears vs. microphones (in your case it may
be related
> to the directionality of the loudspeakers vs. human-speakers).
I suspect
> that better recording equipment and perfecting the
> calibration/balancing/directionality of equipment might help
and of course
> reducing the noise.  I would appreciate hearing about any
answers you find
> through your research.
> To close on a more interesting note, the listeners ability to
localize a
> source certainly must be important to the realness of the
> sensation.  I'm speculating that Doppler shift at walking
speeds would
> probably NOT be detectable for speech sounds especially
considering the
> reverberation in a hall, but it is a thought to ponder.  What
> turbulent air flow noise over the pinna?
> Sincerely,
> Brad Libbey
> Georgia Institute of Technology
> On Wed, 29 Aug 2001, Michael S. Gordon wrote:
> > Dear List -
> >     I am interested in capturing the acoustic flow field of a
person walking
> > down a hallway. Thus far I have made a couple of binaural
recordings of (1)
> > a perceiver walking past individuals reading text (live) and
(2) a perceiver
> > walking past a series of loudspeakers projecting an
assortment of recorded
> > sounds (e.g., human speech, typewriter clicks, etc.). Those
who have
> > listened to these recordings have found the first set a much
more compelling
> > indication of the listener╣s motion than the second. There
are several
> > reasons why this may have been the case: the live readers
were fewer, more
> > sparsely located, and generally louder than the recordings
via loudspeakers.
> >      I am writing to the list because I was hoping that some
of you might
> > have some intuitions or know some references that would help
guide me to
> > more successfully capture the acoustic flow field of a person
> > through a hallway. Specifically I am wondering whether live
sounds should be
> > easier to localize through a loudspeaker than recorded
sounds? Furthermore
> > should the localizability of the sound sources contribute to
the Orealness╣
> > of the walking event for a listener?  I would greatly
appreciate any
> > thoughts on this issue.
> >
> > >             Respectfully,
> > >                 Mike Gordon
> > --
> > Michael S. Gordon
> > Ecological Acoustics Laboratory
> > Department of Psychology
> > University of California, Riverside
> > Riverside, CA 92521
> > USA
> > 909-787-4579
> > mike.gordon@psych.ucr.edu
> >
> >
> >
> >