1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sound Intensities

  1. Feb 23, 2009 #1
    1. The problem statement, all variables and given/known data
    What is the sound intensity 2.5m away from a 50W speaker? (Assume sound is spread out in a sphere) The intensity level 12.0m from a loudspeaker, placed out in the open, is 100 dB, what is the acoustic power output (in Watts) of the speaker?

    2. Relevant equations
    [tex]I =10^{\frac{B}{10} - 12}[/tex]

    [tex]v =\frac{P}{A}[/tex]


    3. The attempt at a solution
    I = P / A
    I = 50 / (4 * pi * 2.5 ^ 2)
    I = 0.64 W / m ^ 2

    If the inensity level is 100 dB, then the Sound intensity is 10 ^ -2 W / m ^ 2.
    So, If I = P / A
    I x A = P
    P = 10 ^ -2 x (4 * pi * 144)
    P = 18.2 Watts

    Is this correct? The 18.2 Watts looks a little for a speaker putting out 100 dB at 12 m...
     
    Last edited: Feb 23, 2009
  2. jcsd
  3. Feb 23, 2009 #2

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Looks good.

    Note that the 50W speaker produces between 110 and 120 dB at 2.5 m, so 100 dB for 18 W is not out of line.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Sound Intensities
  1. Sound intensities (Replies: 1)

  2. Intensity of sound (Replies: 5)

Loading...