Re: FFT - Spectrum Analyzer

[Peter]

On 10-06-2012 00:27, Renato S. Yamane wrote:
> Hi,
>
> Anyone knows an way to analyze, with Octave, the Spectrum Frequency of a 
> digital media file (like an MP3)?
> Something like this: http://img268.imageshack.us/img268/6345/bassiloveyou.jpg
For a long, non-stationary signal, you probably want to estimate the 
power spectral density of the generating stochastic process (lots of 
fancy words). This is done by the computing a "Welch periodogram".

So long story short: type

pwelch(input_signal,hamming(200));

and play aroung with the length of Hamming window until you get the 
display you want. Octave's pwelch does not seem to plot on a dB scale, 
so you might want

plot(20*log10(pwelch(input_signal,hamming(200)));

instead.


Cheers,
Peter.