From: rubaea!lehnert (Hilmar Lehnert)
Subject: Re: Raytracing sound
Date: Thu, 1 Aug 91 11:49:38 MET DST



Hi everybody,

In article (???) mklapman@adsl (Matthew Klapman) writes :

> Subject: Raytracing Sound
> Date: Thu, 25 Jul 1991 09:54:31 GMT
> Organization: University of Illinois, ADSL
> 
> Hello again.  
> 
> I have developed an algorithm that computes three-
> dimensional sound using a raytracing technique.
> This technique allows one to accurately hear sound
> in a 3d world, for example: 
> 
>  (scenario deleted)
> 
> One of my friends told me that there has been some research on this
> subject (some here at the University of Illinois), but I am wondering
> if anyone has been working on this recently, or have something up and
> running.  I have seen the Convolvatron and know about Gehring's 3d
> sound generator, but I do not think these use "sound raytracing."
> 
> Any comments?


Ray-Tracing in acoustics was first used in the early 50th(Allred)
to compute some acoustic paramters of the rooms. The
first room response was computed in 1968 (Krokstadt). Pinna cues
were added to the simulations first in 1987 (Poesselt). There are
at least six comercially available systems on the market which use
ray tracing for the design of acoustic spaces. There are four
systems (research only) that include pinna cues, which allows
listening into the simulated spaces. Another two will be on the
market before long, but this will not be real-time, so its use to
VR is limited.

Real time available-systems that I know are :

    Convolvotron (Scott Foster, Crystal River Eng., PC)
    Focal Point  (Bo Gehring, Gehring Research, Mac)
    BMC          (Klaus Genuit, Head Acoustics, Germany, PC)
    CAP          (AKG acoustics, Austria, HP Workstation)
    RSS          (Roland Spatial Sound System, Roland, Stand alone)

All of that systems use pinna cues to code directional information
into the ear signals. Basically most of this systems simulate no
reflections which corresponds to an anechoic chamber. AKG's CAP is
able to perform a very simple room simulation on the base of free
definable surfaces. If more then one binaural channel is
available, the additional channels can be used to auralize
reflections instead of other sources.
Information on any other systems is very welcome.

Hilmar Lehnert
Lehrstuhl fuer Akustik
Ruhr-University Bochum, Germany
(lehnert@aea.e-technik.uni-bochum.de)