>>  I want to know why white noise floor is added to the autocorrelation
>> function in the lpc analysis.
>
>I'm not an expert with LPC, but I know with adaptive dsp, you need to
>keep the inverse of the autocorrelation matrix stable.  This is
>especially true with highly self-correlated signals.    Injecting white
>noise into a signal before taking the autocorrelation is similar to
>adding a constant to the diagonals of the matrix.  This increases the
>singular values of the matrix which decreases the condition number.  A
>matrix with a lower condition number will invert more accurately (and
>quicker).  However, this comes at the cost of biasing the solution.
>
>http://www.signalsguru.net
>
>

Hey, hope you still remember this conversation, since it is quite old. I
need to know what exactly is the ill behaviour of LPC with pure tones. I
understand that the autocorrelation matrix has a high condition number if
dealing with pure tones ... still it doesn�t seem to produce a problem
with LPC analysis and synthesize. I use sin(x) function, which is (should
be) highly autocorrelated, but the condition number is "only" around
4*10^3.
I think that this simply isn�t big enough to cause trouble during
inversion. Do I need another function ?? 
Thank you in advanve

>  I want to know why white noise floor is added to the autocorrelation
> function in the lpc analysis.

I'm not an expert with LPC, but I know with adaptive dsp, you need to
keep the inverse of the autocorrelation matrix stable.  This is
especially true with highly self-correlated signals.    Injecting white
noise into a signal before taking the autocorrelation is similar to
adding a constant to the diagonals of the matrix.  This increases the
singular values of the matrix which decreases the condition number.  A
matrix with a lower condition number will invert more accurately (and
quicker).  However, this comes at the cost of biasing the solution.

http://www.signalsguru.net

venugopal wrote:


>  I want to know why white noise floor is added to the autocorrelation
> function in the lpc analysis.

This is done to avoid the ill behavior of the LPC analysis when the 
input is close to combination of the pure tones.

> 
> what is the difference between lsp and lsf

Basically the same thing. Just the matter of naming.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

hi,

 I am new to these group.

 I want to know why white noise floor is added to the autocorrelation
function in the lpc analysis.

what is the difference between lsp and lsf

thanks in advance


venugopal