[PD] Ultrasonic 'theremin' patch

Luigi Rensinghoff soundgigi at freenet.de
Thu Aug 7 22:57:09 CEST 2008

Thats very cool...

i heard of someone implementing that with a nord-modular....

If you browse the forums maybe you can find it...

Its a cool thing to have for Sound-Installations...



Am 07.08.2008 um 21:16 schrieb Ico Doornekamp:

> Hi all,
> Yesterday I found out that modern audio cards can do much higher  
> sample
> rates then 48000, which allows for entertaining experiments with
> ultrasound.
> I'm not sure if this has been done before, but I'm pretty happy  
> with the
> results so far.
> I've created a patch running on a samplerate of 88200 Hz, which sends
> out high-frequency chirps over two laptop speakers. The chirps are
> reflected back to the bultin mic using both hands. The reflection is
> correlated with the outgoing chirps to calculate the time the sound
> waves needed to return to the mic, thus measuring the distance to the
> hands or any objects hovering above the laptop.
> This particular patch just drives two tone generators whose  
> frequencies
> depend on the measured distances, which are played back over the same
> speakers as the high-frequency chirps. The result is a
> two-tone-polyphonic theremin-like instrument.
> If only I could play this thing in tune...
> A simple demonstration video and the patch can be found at
>   http://zevv.nl/play/code/ultrasonic-theremin/
> This patch just a first test using ultrasound, I'm sure much more
> interesting things can be done using this technique.
> The patch is not very well documented at this time, and I think  
> getting
> things to work needs a fair amount of tweaking for each different  
> setup.
> Things that need to be setup properly are output level of the  
> soundcard,
> a magic gain factor after the correlation, and the range that  
> should be
> inspected for echo peaks to avoid detecing of reflections from the
> ceiling.  I think it would be possible to make the patch do some
> auto-detection of some of the paremeters like ceiling height and gain
> factors, which would make a nice addition for future versions.
> Enjoy,
> Ico
> -- 
> :wq
> ^X^Cy^K^X^C^C^C^C
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