Thanks for the feedback! I guess I have to think what I want to do and how to do it. On the issue of doppler effect, wouldnt that work based on the fact that when the sound from the speaker moves towards you it will have a higher pitch than the sound when it goes away from you? Sound is sound and it travels at the speed of sound...? Its quite some time since i did physics at highschool

Ill do some more research on the subject and post it here when i have something to tell...