[AG-TECH] Sound localisation work?

Osland, CD (Chris) C.D.Osland at rl.ac.uk
Thu Nov 28 07:32:14 CST 2002

It was a subject I attacked during a short sabbatical in Germany
a few years ago for a thing called the Communication Wall - a VR
+ video keying approach to the same sort of problem as the AG
aims to tackle.

One of the problems that dogged that project was that as they were
using hard surfaces for the rooms (they used rear-projected stereo
projectors) there was a disastrous amount of secondary reflections
of any sound source.  I draped carpet over the side walls (not used
for projection, but they happened to be plasterboard and so hard)
and improved things a lot.

There are many problems to solve in the AG context:

1.	non-unique views of participants:

If a person is visible in more than one view, where should the
virtual sound source corresponding to that person be positioned?

2.	multiple people viewing/hearing at each site

There is basically no known solution to the problem of how to
create a sound field that is the same for several people, unless
you put headphones on each person AND headtrack them.  The problem
can be partially solved by using phase differences more than
amplitude differences (this is done by the TiMax system used in
theatres) but the normal layout of an AG node makes this difficult
to achieve - the physical distances are too small.

3.	the rooms have to be excellent acoustically before you start

This is really the same point as I made above concerning reflective
walls - if there are uncontrolled reflections, any effort put
into generating localized sound is wasted.

I created a website about my project and will try to get that
up somewhere - I think it's fallen off the edge of our web
for the present.

I'll try to find references to things like

	TiMax - the theatre system - they were at

Robin Whittaker
Out Board Electronics Ltd
T: +44 (0)1223 837827
F: +44 (0)1223 837798

			but went into receivership some months ago;
			I think Robin has hooked up with another firm
			to try to keep TiMax going

	Crystal River - people who make sound localization cards for PCs

and the places where I found out stuff for my sabbatical.  It looks
as though Crystal River have gone belly up as well.

	A couple of useful links are

and	http://www.anu.edu.au/ITA/ACAT/Ambisonic/Spatiallinks.html



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-----Original Message-----
From: Michael Daw [mailto:mike.daw at man.ac.uk]
Sent: 28 November 2002 12:52
To: AG Technical Developers
Subject: [AG-TECH] Sound localisation work?

I'm just wondering if anyone knows of any work going on to do with sound
localisation in the AG? I'm thinking particularly of development to help
locate where peoples' images are on the screen and in holding simultaneous
conversations between sites, or anything related.

I'd be grateful if someone could provide contacts (if any).



Michael Daw
SVE Group (Supercomputing, Visualization and e-Science)

Manchester Computing, Kilburn Building,
University of Manchester, Manchester M13 9PL, UK

Tel: +44 (0)161 275 7026
Fax: +44 (0)161 275 6800
Email: michael.daw at man.ac.uk


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