Re: fft and wavelets

[Peter L. Soendergaard]

On 2012-08-23 11:32, Sergei Steshenko wrote:
> I can use fft to get the, frequencies, phases and magnitude of a loaded 1 second audio 
> file of person saying "ahhhh" and recreate it.
> What I'm trying to do now is find out where each of those frequencies begin and 
> where they stop in the 1 second audio file
>
>
>
> Example:100hz starts at .23seconds to .34seconds,
> 104.34hz starts at .35seconds and ends at .37seconds.
>
> Can fft's do this or do I need to shift my whole program to use wavelets?  Also 
> are there any wavelet examples in octave that show how do this?
No, fft cannot do this because it does not simultaneously encode time 
and frequency information. Wavelets will solve you problem, but it is 
perhaps a little overkill

A spectrogram should solve your problem. Call the "specgram" command, it 
is in the "signal" package, it will should a nice image.

You can also install LTFAT (google it) and call the "sgram" command.

Cheers,
Peter.