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Thread: The speed of sound?

  1. #1 The speed of sound? 
    Forum Cosmic Wizard icewendigo's Avatar
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    As a kid I saw a jetfighter pass at low altitude faster then the speed of sound, I will never forget it, the plane flew by in complete and absolute silence, like an illusion, it was still silent after it passed by, a good moment later I could hear far, far in the distance where the plane had come from the faint noise of incoming jet approaching and becoming louder as it got closer, until it passed with shattering force chasing the ghostly plane that had flown by earlier.

    So my question is, if a plane is so fast and so far in front of the sound it generates, does the pilot even hear the engine noise?

    If he doesnt hear the engine, does every noise comming from up ahead become shifted and everything behind become silent? I guess the pilot doesnt hear the engine noise generated in the air outside thats left behind but hears sounds generated within the envelope of matter (plane structure, cockpit air) he is part of and traveling in. hum, ok I think I get it. Not being part of that moving envelope was why I did not hear the plane as a kid until after it had passed. hum


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  3. #2  
    Forum Bachelors Degree
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    OK, you answered your own question. And you got it right.

    Incidentally, the plane that you observed from the ground did not necessarily exceed the speed of sound. (Many localities have regulations prohibiting supersonic speeds below a certain altitude. They wish to avoid damage from the sonic boom.) Even if your plane were travelling at just under Mach 1 you would still observe the same effect, that its noise had to catch up.
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