Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Sound Waves from a loudspeaker

  1. Oct 16, 2003 #1
    I've been stuck on this one problem for a bit, any help is really appreciated.

    "A loudspeaker is placed between two observers who are 110m apart, along the line connecting them. If one observer records a sound level of 60.0 dB and the other records a sound level of 80.0dB, how far is the speaker from each observer?"

    I've been having a tough time grasping sound waves in general actually. These problems usually take me alot longer than the previous chapter on wave motion. So I was also wondering if anyone knew some good help sites with sound waves, I seem to only find ones with formula's on them.
     
  2. jcsd
  3. Oct 16, 2003 #2
    My guess is that the decibel scale was created for just such a problem. That is,

    80~P/x3.2 and 60~P/(110-x)3.2

    where P is the power at the speaker, x is the distance for the 80dB observer, (110-x) for the 60dB observer, and the approximation that the sound intensity drops off as the 3.2 power of distance is assumed. (Remember, 23.2=10) Solve the two equations by eliminating P.
     
  4. Oct 16, 2003 #3
    thanks alot!
     
  5. Oct 16, 2003 #4
    I hope I'm right, Lipd.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook