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!

Homework Help: Power of Sound Wave at distance

  1. Jun 3, 2015 #1
    1. The problem statement, all variables and given/known data
    A sound source is placed at the top of a (h = 121.5m) radio tower. The source has a frequency of 653.8 Hz and an amplitude of 11.4 nm at point A. The air surrounding the tower has a density of 1.32 kgm-3 and sound travels through it with a velocity of 340 ms-1. Point A is 10.8 m above the source. You may ignore any reflections of the sound from the ground.

    2. Relevant equations
    P = (1/2) ρAv (ω s( max ) )^2

    3. The attempt at a solution
    Determine angular velocity from frequency. Sub in density and velocity.
    I think A means amplitude and I would put in 11.3nm.
    However, s(max) is "displacement amplitude". Does this mean that s(max) = 11.4nm and A= distance from Point A to sound source?
  2. jcsd
  3. Jun 3, 2015 #2
    Have been doing some research. A seems to refer to area of the wave sound. So would I be correct in putting A as 4 Pi r squared? Assuming sound is moving out as a sphere?
  4. Jun 3, 2015 #3
    This is indeed the correct method for anyone else who has trouble with this question.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted