room impulse response and deconvolution

[Martin Czech]

:::When I use this I use a signal which autocorrelation is a single pulse, thus
:::basically acting in for the dirac delta. Now, knowing the autocorrelation is
:::so nice to us, we can use the cross-correlation of the signal source and the
:::resulting signal from the output of the linear system. A room can be


SNIPPED

Ok, just to be sure:

On one hand you have the balloon sequence, B.
Your hope is that the autocorrelation B##B is a unit inpulse.
On the other hand is the room sequence R, which is 
the convolution of the ideal room sequence Ri and the balloon
sequence B, ie.

R=Ri**B

you say that if you apply the correlation with B on both sides

B##R=Ri**B##B

the autocorrelation of B appears, and this is the unit impulse UI,
so 

B##R=Ri**UI=RI

so the correlation of the Balloon response B with the measured
room response R is the desired ideal room response Ri.
All by linearity and time invariance.

Great!

Unfortunately B looks very strange, this may be due to the microphones.
It looks like a damped sinusoid, with very low frequency, some 10Hz.

So B##B will NOT look like UI.

If you are interested, I could send you a gnuplot style data file.


I guess I need better microphones, phase linear.


:::Well, diffusion is nice, when you want it. If you want a clearer responce noise
:::could be an issue.

It is a noise floor, low level, this will translate into a very low
diffusion level, and this is not audible, because of masking.
Convolution means also gating, no signal , no noise.

And: a sine signal (critical in all other situations) convolved with some
noisy filter sequence (long enough, so that the noise becomes audibl
as such) is really a filter, only noise arround the sine will get through,
but this is masked, also. 

m.c.