90-06/binaural.stereo.work
From: "Michael John Muuss <mike@BRL.MIL>" <mike@BRL.MIL>
Subject: Re: Binaural stereo
Date: 17 Jun 90 03:20:09 GMT
Organization: Ballistic Research Laboratory




In article <IaRe8sG00W0O42uXZG@andrew.cmu.edu>, aj14+@andrew.cmu.edu
(Andrew David John) writes:
|> 
|> If a computer could reproduce the echo/frequency-shifts/etc... that occur 
|> when sound comes from a given direction and passes by the head, then it 
|> could breate synthetic binaural stereo.
|> 
|> Does anyone know if the positioning mechanisms of the human auditory system 
|> are understood?

I refer everyone to the excellent work being done at NASA/Ames by Elizabeth
Wenzel and Scott Foster.  I saw their equipment demoed at the 1990 Symposium
on Interactive 3D Graphics (Snowbird Utah, March 1990), and the audio
effects were very well done.

Their aparatus was a Sennheiser HD-540 Pro headphone with a Polhemus 6 DoF
tracker cemented to it, and another 6 DoF tracker for you to hold.
A PC & a snazzy custom DSP board took a monaural sound source (in the
demo, from a CD player) and positioned it to "seem" like it was located
at the hand-held tracker.  Move either your head or the tracker, and
a pretty good approximation of the "right" effect happened.

The Head-Related Transfer Function (HRTF) is synthesized from 144 pairs
of Finite Impulse Responses (FIRs) measured for the sample head.

Superb work.  Read about it in COMPUTER GRAPHICS, V 24, Number 2, March 1990
"A publication of ACM SIGGRAPH, special issue on the 1990 Symposium on
Interactive 3D Graphics".  pp 139-140.

        Best,
         -Mike Muuss

          Advanced Computer Systems
          Ballistic Research Laboratory
          APG, MD  21005-5066

=====

Blauert, Jens, 1983.  _Spatial Hearing: The Psychophysics of Human Sound
	Localization_, Cambridge, MA: MIT Press

Wenzel, Elizabeth M.  'Localization in Virtual Acoustic Displays,'
	_Presence_ 1st issue.

Wightman, F.L. & Kistler, D.J. 1989a,b.  'Headphone Simulation of Free-field
	Listening I, II.'  _Journal of the Acoustical Society of America_,
	_85_, 858-878.
