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Homework Help: Need Help-Sound

  1. Nov 8, 2005 #1
    I need help for this problem. I tried applying the formula B=10log(I/Io) but I don't get right answer. Someone help me or give me suggestion/hint about what to do? The problem is as follows: At a rock concert, a dB meter registered 130gB when placed 2.8m in front of a loudspeaker on the stage. a) What was the power output of a speaker, assuming uniform spherical spreading of the sound and neglecting absorption of air? b) How far away would the sound level be a somewhat reasonable 90 dB?
     
  2. jcsd
  3. Nov 10, 2005 #2
    what answer do you get?
    I would have thought that you would use the decibel equation you have to solve for I. Then once you have the intensity you can solve for [tex]P_a_v_e[/tex] given that you know the distance away from the source and that it is spherical spreading with no attenuation through air.

    I=P/A

    Where A is the surface area of a sphere: [tex]4(\pi)r^2[/tex]

    Does this give the wrong answer?
     
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