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room reverberation simulations

> Date:    Tue, 26 Feb 2002 22:36:56 -0800
> From:    John Hershey <jhershey@COGSCI.UCSD.EDU>
> Subject: simulated reverberation
> What is the most natural way to computationally simulate realistic
> reverberation?
> I am told that real reverb is non-linear, due to the moving around of
> air, so you in principle you can't just run it through a linear filter

It is true that in a large room that the impulse response will vary with
time, due to air currents, fluctuations in temperature, and the like.
However this is not a nonlinear effect, it is rather a time-varying
effect. To be nonlinear, the signal would need to interact with the impulse
response. That is not an effect one must worry about normally. The
sound in a horn loudspeaker might become nonlinear, but not the room
impulse resp.  I wouldn't worry about the time varying effect either,
unless you wish to attempt to invert the impulse response, or you
want to simulate an auditorium.

There is a matlab version of my room image program on the net.
I cannot attest to its accuracy (The JASA fortran prog has no known
bugs, that I know of)



Look at:

   author = {Allen, J. B. and Berkley, D. A.},
   title = {Image method for efficiently simulating small-room acoustics},
   journal = JASA,
   volume = {65},
   pages = {943-950},
   year = {1979}

and maybe

   author = {Neely, S. T. and Allen, J. B.},
   title = {Invertability of a room impulse response},
   journal = JASA,
   volume = {66},
   pages = {165-169},
   year = {1979}

Jont B. Allen, 973/360-8545 voice, 775/796-9844 (fax), 908/789-9575 (home fax)
Technology Leader Speech Processing Software and Technology Research
http://www.research.att.com/~jba; http://auditorymodels.org/jba
Room E161, AT&T Labs-Research, Shannon Laboratory
180 Park Ave., Florham Park NJ, 07932-0971

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