Hi everyone, as part of a symposium project I am creating an audio experience meant to model the ambient sound of a city with pure data. I have been looking into creating the doppler effect for the cars in my patch. I'm trying to implement 2 patches using a variable delay line to derive a doppler effect. (I am ending from the car patch to dopvelocity and then doppler delay to dac~... It does not seem to work. Could anyone shed any light on this?

Cheers,

Will
dopvelocity.pd dopplerdelay.pd

Hello Will...... There are bits missing from your posted patch I think.... so hard to tell.
You need a pitch shift. Here is an excellent page for understanding the principles involved...... http://katjaas.nl/pitchshift/pitchshift.html
In the Pd doc/audio.examples folder the [B12.sampler.transpose] patch will give a Doppler effect as the chunk size is changed.
David.

Hi,
I'm not sure what onepole~ is so I didn't look @ the patch too much, but I believe a doppler effect could be achieved simply by calculating the distance of the sound source from the listening location and then putting the amount of time that it would take sound to travel that far into vd~. So, if sound travels 343 m/s on average and your sound source is 343 meters away you would put 1 second into vd~ and update vd~ with line~ whenever the sound source's position changes. That should create a pitch shift effect automatically

However the situation becomes more complicated with multiple sound sources as you'll need multiple delay lines. At that point memory usage would be something to consider, and perhaps the possibility of using a single delay line for all sound sources