regarding white noise

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

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

>  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

>>  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