Doppler Shift - Yee yummmmm...... - The Unofficial BMW M5 Messageboard (m5board.com)

willm5ad · 16th October 2005, 22:04

Just reading a very interesting book by Bill Bryson - A short history of nearly everything and found the reason for the above noise, as follows:
Named for Johann Christian Doppler an Austrian Physicist, who first noticed the effect in 1842. Briefly what happens is that as a moving object approaches a stationary one its sound waves become bunched up as they cram up against whatever device is receiving them (your ears, say), just as you would expect of anything that is being pushed from behind towards an immobile object. This bunching is perceived by the listener as a kind of pinched and elevated sound (the Yee). As the sound source passes, the sound waves spread out and lengthen, causing the pitch to drop abruptly (the yummm).
So next time you see and hear an M5 passing at speed you will know what the sound is called. I am sure some of our scientists can elaborate on this theory.
WillM5AD

BmwNut · 17th October 2005, 06:24

Gotta love it. Works with radar too, and is always a handy excuse to an officer who doesnt know too much about physics (even though most modern detectors are accurate, even with the doppler shift).
What I want to do if find the correct pitch change in my voice to null out the shift. How scary would it be if you passed a car with someones head sticking out the window, and all you hear is "AAAAAHHHHH."

Code3M5 · 17th October 2005, 10:33

Read the book...loved it!