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regarding white noise

Started by venugopal December 21, 2005
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