[PD] Ultrasonic 'theremin' patch
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 ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Ultrasonic 'theremin' patch
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... Best Luigi 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 ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/ listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
