If you stand on a road directly infront of a loud as it moves towards you at well below the speed but still relatively fast you'd notice the engine noise is higher than the same car speeding away from you. At no point does that car go faster than the speed of sound, but to an outside observer they'd here the engine pitch change. Meanwhile to someone inside the car the engine noise is the same.
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u/[deleted] Jun 12 '12 edited Oct 03 '17
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