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Homework Help: Trumpet players, sound intensity level

  1. Jan 29, 2010 #1
    1. The problem statement, all variables and given/known data

    Five trumpet players have a sound intensity level of 75dB. What would be the sound intensity level of 30 such trumpet players? _______dB


    2. Relevant equations

    Increasing the sound intensity by a factor of 10 results in an increase in perceived loudness by approx. a factor of 2.

    Beta = (10dB)log10(I/I0)
    Where I0 = 1.0x10-12 W/m2


    3. The attempt at a solution

    I tried finding a ratio and applying that to the 2nd situation but my answers were wrong. Can someone please help me ASAP!!

    Thank you!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 29, 2010 #2

    ideasrule

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    Homework Helper

    10 dB=1 bel, and that's 10^1. 100 dB=10 bel, and that's 10^10. 75=7.5 bel, which is equal to what power of ten?
     
  4. Jan 29, 2010 #3
    0.75?
    3/4?
     
  5. Aug 19, 2010 #4
    The 30 trumpeters will be 6 times greater intensity than the 5 trumpeters. The ratio in decibels all "drop out" leaving log(6) = 0.78 (about).
    30 trumpeters are louder than 6, so to get the new decibels it is 75 / 0.78 = 96 decibels.

    Logic check - 6 x intensity is < 10 x, so we expect the difference in decibels to be < 2x.

    cheers!
     
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