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Old 05-30-2011, 07:13 PM   #783
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Moseph's Avatar
Join Date: Jul 2003
Posts: 2,875
Originally Posted by ares View Post
I'm familiar with this equation, I actually use a modified version (Eyring) to calculate the reverb times in my simulation system.

The point that I'm getting at is that in most cases, the response of a room/source/listener configuration can be described by an impulse response: convolve this IR with source audio of any amplitude and you're going to get the same result times the input audio gain coefficient. The response is linear with respect to the energy of the sound source in most cases.

There are certain non-linearities w.r.t. energy that deal with how the sound interacts with air as it travels as well the interactions with materials in the room, but these are probably so small that they wouldn't have any effect when mixing at different volumes.
I'll see if I can't dig up something about the Eyring model in books/journals. This is one of my weakest areas regarding the physics/math of the situation. Admittedly, it's kind of rough in general to learn this stuff just because so much is happening in the math domain that it's hard to follow without sitting down and working through derivation yourself (and who wants to do that in their free-time?).

Refresh my memory: convolution (in the time-domain) is linear with respect to energy/frequency response, but non-linear with respect to transient response, correct?

I also can't remember the other properties that comprise linearity (if memory serves, it's more than just scalability), but I'm willing to take your word on it.

Originally Posted by ares View Post
Yes, my simulation system can use arbitrary geometry and every surface has material properties that specify the absorption at different frequencies. If you'd like to read about it, here is a paper I presented earlier this year at the 41st AES conference in London:
Cool beans, man. I'll take a look at this when I have some free time.

Last edited by Moseph; 05-31-2011 at 07:12 AM. Reason: Spelling Error
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