Radar, Laser, and [i]Sound?[/i]

[95ProLeila]

Totally passive system, and therefore undetectable/unjammable:
http://www.leftlanenews.com/2006/04/27/new-speed-traps-could-measure-speed-based-on-sound/

[Intruder]

Just for clarification... Most of the people who posted comments after the article think this system is based on the loudness of your exhaust. It's not. The system monitors the rate of change of frequency as the vehicle approaches. This is called the Doppler effect. This is exactly what changes the sound of, let's say an ambulance's siren as it approaches you and passes by. As the vehicle approaches, the sound waves are compressed (higher frequency), as it drives by and goes further away from you the sound waves are spread out (lower frequency). Doppler shift.

[95ProLeila]

Just for clarification... Most of the people who posted comments after the article think this system is based on the loudness of your exhaust. It's not. The system monitors the rate of change of frequency as the vehicle approaches. This is called the Doppler effect. This is exactly what changes the sound of, let's say an ambulance's siren as it approaches you and passes by. As the vehicle approaches, the sound waves are compressed (higher frequency), as it drives by and goes further away from you the sound waves are spread out (lower frequency). Doppler shift.

yeah, the headline for the article spooked me, but then I read it, kind of a neat concept . . . even if it does suck.