[PD] Detecting the bpm of an audio input

[Mathieu Bouchard]

On Fri, 29 Nov 2002, arm pdlist wrote:
> No comes que question. I have a small mic that i
> connected to my laptop. I can get the signal in PD.
> But how can i detect the bpm of a signal that is
> coming from adc~ object? I'm just touching on the mic
> to simulate the heart beat, but would be possible to
> detect some kind of bpm of the signal? If so, what do
> i have to do? Can you give some links where i can get
> some more info on what i should do?

My first idea would be to try a Fourier transform but with very low
frequencies. When trying this on music you may have some preprocessing to
do to ensure that you actually get a spectrum for the beat instead of just
for the hearable tones, but for a heartbeat you have true low frequencies
that could appear directly in an "ordinary" frequency spectrum as long as
that spectrum is done in the proper range of frequency (say 0.1-10 Hz
instead of the normal 20-20000 Hz).

I haven't tried it myself though.

________________________________________________________________
Mathieu Bouchard                       http://artengine.ca/matju