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Homework Help: Doppler Effect (Sound)

  1. Jan 22, 2009 #1
    You are standing on railroad tracks as a train approaches at a constant velocity. Suddenly the engineer sees you, applies the brakes, and sounds the whistle. What do you hear starting at that moment?

    Because the waves are "stretching" as it approaches you slower and slower, I said that the "loudness increases, and pitch decreases." Is this correct?
  2. jcsd
  3. Jan 22, 2009 #2


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    Sounds good to me. As the train approaches you at slower and slower speeds, the apparent frequency of the sound would decrease.
  4. Feb 16, 2009 #3
    But doesn't the fact that it's still approaching you make the pitch seem like its increasing regardless of acceleration?
  5. Feb 16, 2009 #4


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    The fact that there is velocity increases the frequency over what it is on the engine, ... but the gradient of velocity is decreasing the amount at which the frequency has been increased - i.e decreasing.
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