http://www.geocities.com/nk7jaffna/a...lpdesk/xxx.doc



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Speaker transmit 1000Hz sine wave signal.
If vehicle is not move, human heard 1000Hz frequency.
But if vehicle move constant velocity is the human heard frequency change or same?
(is sound wave’s velocity in the enclosed vehicle is depend on vehicle’s speed?)

What exactly is this?

I'm not sure what you're asking but I'll have a try:

If the speaker is moving with the car, and the ear is moving with the car, then the speaker and the ear are moving at the same speed, and there is no doppler shift.

Doppler shift occurs when the source or the detector are moving relative to each other at a speed that is a significant fraction of the speed of the wave in the medium between the source and the detector.

In the case I think you are using, the relative speed between the speaker and the listener is 0.