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Generate a silence

  1. Oct 10, 2004 #1
    Hi,
    I'm wondering If we could generate homogeneous sound field and if we put two sound sources which would have inverse phaze we could attain silence.
    Is it possible to do that?
    Is it possible to generate homogeneous sound field in a room full of moving objects (people)?
    Regards,
    Niko
     
  2. jcsd
  3. Oct 10, 2004 #2
    isnt that how a muffler works?
     
  4. Oct 10, 2004 #3
    n/m i misread the question
     
  5. Oct 10, 2004 #4
    Yes, but that sound isn't much complex. Actually I was tinking about realizing a room with two melodies playing each in a part of room without mutual disturbance.
     
  6. Oct 10, 2004 #5
    you watched batman beyond didn't you....:P

    To be truthfull, I can't help you, I just couldn't resist posting though...;)
     
  7. Oct 10, 2004 #6

    HallsofIvy

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    Theoretically, you could but only at the point exactly midway between the two speakers but nowhere else and not if there were objects between.
     
  8. Oct 10, 2004 #7

    NoTime

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    They do sell earphones that work fairly well using active sound cancelation.
     
  9. Oct 11, 2004 #8

    Alkatran

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    You could do it at any point. The problem is making it work for all points.
     
  10. Oct 11, 2004 #9

    HallsofIvy

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    I remember a science fiction in which a person built a machine that would analyze incoming sound waves and broad cast a "cancelling" signal. Of course that couldn't work. it would be already "too late" for points between the sound source and the machine and even for points further down the line, the fact that it would require some time to analyze means that the machine would not be able to cancel the sound.

    In the story, teenager who were deprived of the rock and roll constantly in their ears (today, rap?) found they had to actually THINK and, of course, immediately went crazy!
     
  11. Oct 11, 2004 #10

    Alkatran

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    Well the machine would analyze at one end and broadcast at the other. Too bad the 'cancelling' sphere and 'actual' sphere for the sounds could never exactly match up... and you'd just end up doubling the noise.
     
  12. Oct 15, 2004 #11

    LURCH

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    Thsi sounds similar to the earphones NoTime mentioned; they are no longer science fiction, and as some have been made. Last I heard, there was talk of making them standard issue for airport employees, but I don't think their use is very widesperad, ATM.
     
  13. Oct 15, 2004 #12

    russ_watters

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    Ain't technology great: Google: noice cancellation headphones? Its not star trek, guys, its for real and the technology isn't all that complicated (though its still pretty cool).

    Halls - midway between the two speakers is exactly where you locate your head between headphones. Also, the speed of sound is slow compared with the processing speed of computers. No, you can't cancel out the cycle that's being analyzed, but the next one or the one after that you can. So it works great for relatively constant sounds - the primary application of this is airplanes.
     
    Last edited: Oct 15, 2004
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