[linux-audio-announce] Mic-In-Room Simulator

davidrclark at earthlink.net davidrclark at earthlink.net
Sun Feb 26 12:18:32 EST 2006

Greetings to all,

Announcing grad_Boxster for creating impulse response functions 
(IR's) for rectangular parallelepipeds --- for example concert 
halls modelled as giant boxes --- but using the *gradient* of the 
solution field projected on a direction specified by the user, 
similar to the operation of a pressure-gradient microphone ---  in 
a room.

At the URL below is a link to this package for downloading as well 
as a NON-optimized, alternating demo of grad_Boxster versus 
Boxster (i.e. "ordinary stereo versus binaural" or even "speakers 
versus headphones"): 


grad2_Boxster is also available for simulating second-order mics 
in rooms.  Extending grad_Boxster, the gradient of the first-order 
projection is computed and projected onto a second direction 
specified by the user. 

By combining IR's from Boxster (pressure mic), grad_Boxster 
(first-order mic), and grad2_Boxster (second-order), it should be 
possible to simulate any type of mic setup and combination of 
setups in any room that could be considered to be a box.  Starting 
with dry, monophonic recordings made in a dead room, one should be 
able to simulate very sophisticated mic setups in a concert hall, 
then assemble them into a mix, simulating an ensemble recording, 
all with a physically consistent model.

The demo contrasts simulation of nearly coincident pressure-
gradient mics (grad_Boxster) in a 12,500 m3 concert hall versus 
binaural omni pressure mics (Boxster, no HRTF) in the same hall 
with the same separation between mics for both.  The only 
difference for the first half of the demo is whether or not the 
gradient is computed, yet the sounds are very different both with 
speakers and with headphones (esp. the latter).  In the second 
half, the positions of the guitars are slightly different (maximal 
separation for either).


In short, grad_Boxster can be used to simulate ordinary stereo 
recordings (Blumlein, etc.) in the same manner that Boxster can be 
used for simulating binaural recordings, complete with reverb, echo, 
stereo separation, and so on --- but with physical consistency.  As 
a side effect, both new programs provide other "knobs" for extending 
sample generation capability.  All programs can be run either from 
a PyGtk GUI or from the command line.

Regards to all,

Dave Clark

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