how to use periodogram?

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.

Answer 1

[Wayne King]

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.

Answer 2

[nah]

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

[Wayne King]

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]

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??