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Problem on Doppler effect and sound level

  1. Jul 5, 2016 #1
    1. The problem statement, all variables and given/known data
    A source emits a spherical sound wave at frequency ##f=110Hz## with power ##P=1 W## in a solid angle of ##2 \pi sr##. An observer moves with velocity ##v_{oss}=108 km/h## towards the source. Determine the sound intensity level received by the moving observer.

    2. Relevant equations
    Doppler effect and sound intensity level

    3. The attempt at a solution
    I just do not know how to approach the problem because it is very different from a common Doppler effect problem.

    The frequency perceived by the observer is ##f'=f(\frac{c+v_{oss}}{c})## but this does not give me the sound intensity level

    To find the sound intensity level means to find the intensity. Now, the intensity of a sound wave is ##I= 2 \pi^2 f^2 A^2 \rho##.

    Plugging ##f'## in the formula for ##I## does not give the correct result and there must be something that I am missing. How to do such exercises?
     
  2. jcsd
  3. Jul 5, 2016 #2
    You need to define all the variables.
     
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