power spectral density via LPC
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Tomas Fridrich
on 11 Nov 2013
Commented: BAPPA MUKHERJEE
on 19 Jan 2014
Hello,
I have question about LPC spectrum. I would like to compute LPC of given signal and compare it with PSD
x=loadbin('ma004009.ils');
fs=16e3;
tt=(0:slen-1)./fs ;
slen=length(x);
NFFT=slen;
y=fft(x3,NFFT);
Pyy=y.*conj(y);
Pyy=10*log10(Pyy); % PSD of signal
LPC spectrum
[en,a]=lpc(x,10);
N2=fft(en,NFFT);
Puu=N2.*conj(N2)/NFFT;
Puu=10*log10(Puu);
this gives me PSD of signal via LPC but the curve is upside up. why? And how to fix it? Thanks for any ideas.
Tomas
Accepted Answer
Wayne King
on 11 Nov 2013
You want to multiply by -1 because its 1/Puu. For example:
load mtlb;
x = mtlb.*hamming(length(mtlb));
a = lpc(x,12);
NFFT = 2^nextpow2(length(mtlb));
lpcDft = fft(a,NFFT);
lpcDft = lpcDft(1:NFFT/2+1);
plot(-20*log10(abs(lpcDft)))
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