how to use periodogram?

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nah
nah 2012-10-2
i want to analyse a .wav file using spectral.periodogram, but i have a trouble, what should i do?
x = wavread('balaclava5s.wav'); size(x); N = 350208; Fs = 44100; ts = 1/fs; tmax = (N-1)*ts; t = 0:ts:tmax; periodogram(x)
is it right? i'm new to digital signal processing, and i have no basic.

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采纳的回答

Wayne King
Wayne King 2012-10-2
编辑：Wayne King 2012-10-2
wavread() will return the sampling frequency. Then you input the sampling frequency into periodogram() (along with the other documented inputs) to get a meaningful frequency vector as an output.
[x,Fs] = wavread('balaclava5s.wav');
[Pxx,Freq] = periodogram(x,rectwin(length(x)),length(x),Fs);
plot(Freq,10*log10(Pxx))
grid on;
xlabel('Hz'); ylabel('dB/Hz');
Just
periodogram(x,rectwin(length(x)),length(x),Fs);
produces a plot without outputting any data.

更多回答（1 个）

nah
nah 2012-10-2
thankyou for your help, but i got these errors:
??? Error using ==> times Matrix dimensions must agree.
Error in ==> computeperiodogram at 55 xw = x.*win;
Error in ==> periodogram at 116 [Sxx,w] = computeperiodogram(x,win,nfft,esttype,Fs);
Error in ==> Coba at 2 [Pxx,Freq] = periodogram(x,rectwin(length(x)),length(x),Fs);
i don't know what those mean or how to fix it
  2 个评论
Wayne King
Wayne King 2012-10-2
编辑：Wayne King 2012-10-2
You likely have a two-channel recording from the .wav file.
Try this
[x,Fs] = wavread('balaclava5s.wav');
x = x(:,1);
[Pxx,Freq] = periodogram(x,rectwin(length(x)),length(x),Fs);
plot(Freq,10*log10(Pxx))
grid on;
xlabel('Hz'); ylabel('dB/Hz');
Then the rest of my example.
nah
nah 2012-10-3
oh my dear, it works!!! thank you so much for your help, thank you. may i ask something? what are those 2nd, 3rd, and 4th line for??

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