WINDOWS USERS: I don't think this will work for you, because I used the java vector math libraries, and it turns out those aren't installed by default on your computers. At least that's my theory, anyways, until I fix it you'll just have to go without the doppler effect. Sorry.
Simple Doppler effect simulator. Drag the sliders to change the speed of "sound", the frequency of the source, and the resolution of the simulation. The velocity of the source, and hence the amount of doppler shifting is determined by its distance from the center. Click to reposition it.
Source code: doppler
Built with Processing