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Homework Help: Question involving beats and sound waves

  1. Sep 12, 2005 #1
    Hi, I have a question involving beats and sound waves.
    When two sound waves (one with a MUCH LARGER Frequency than the other) combine, what would happen? Would there still be a beat pattern? Me, I think that if there still is a beat pattern, it would have the same frequency as that of the highest frequency of one of the combining waves. Am I right, or horribly wrong? I'm really puzzled by this. Thank you very much for your time.
  2. jcsd
  3. Sep 12, 2005 #2

    Tom Mattson

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    Check your book and find the formula for the beat frequency. It is not the higher of the two combining frequencies.
  4. Sep 12, 2005 #3


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    If wave #1 has a much larger frequency than wave #2, then what you get is (approximately) a wave of frequency #1 whose amplitude varies according to frequency #2. This is the principle used in AM (amplitude modulation) radio signals.
  5. Sep 12, 2005 #4


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    IMO, the answer can be seen clearly by looking at the "unmanipulated" equation of "beats", i.e. the simple addition of the two waves:

    [tex]y(t) = Acos(\omega_1t) + Acos(\omega_2t)[/tex]

    what does the addition of these two graph looks like if [itex]\omega_1 << \omega_2[/itex]?
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