On 4/30/2010 7:02 AM, Invisible wrote:
> Mike Raiford wrote:
>
>> It's amazing when you look at how your auditory system works. Your
>> brain essentially gets the Fourier transform of what you're listening to.
>
> Be careful with that...

Yeah, I was simplifying greatly what is happening... If you want to 
display a voiceprint or Realtime spectrum, you'll need to move a window 
across the signal.

> (You might think, for example, that you could just snip your 5-minute
> song into, say, 50 ms chunks and take the Fourier transform of each
> chunk. Alas, snipping it up introduces phantom frequencies that aren't
> really there.)
>
> I've spent a significant amount of time trying to come up with some
> mathematics for analysing sound the way that the human auditry system
> does... So far, nothing works.

Yeah, someone said it before, but there are windowing functions for 
that. If you want to get quick and dirty, you can use a rectangular 
window, but this will introduce artifacts in the resulting spectrum.

Strangely enough the other day I was experimenting with windowing in a 
Fourier transform to analyze a rather complex FSK signal (Trying to get 
a grip on how the signal worked ...) The major problem I had with it was 
the fact that there was significant smearing between samples, that I 
couldn't tell when the frequencies were changing, not only that it made 
it exceedingly difficult to determine what the frequencies were. I tried 
various windowing functions and window sizes.

I should pick up my little DSP project I was working on and fiddle with 
it again.

-- 
~Mike

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