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Acoustics->porous sheet in front of a wall, what is the incident sound power absorbed

  1. Dec 17, 2009 #1
    1. The problem statement, all variables and given/known data
    A sheet of porous material is suspended in air at a distance of 1/4 wavelength in front of a rigid wall. For the frequency of interest, the mass of sheet is high enough not to move significantly under the influence of a sound wave. When a constant frequency plane wave is normally incident on the sheet, a microphone behind it at the wall surface registers an rms value of 0.2 Pa.
    What is the specific flow resistance of the sheet?

    2. Relevant equations

    Vfront-Vsheet=Vback-Vsheet= (1/Rf) x (Pfront-Pback)

    Pback=0.2 Pa (Given)
    We need to find Rf=specific flow resistance.

    3. The attempt at a solution
    I think that Vsheet=0 since the pressure is not enough to move the sheet.
    we dont know Pfront.
  2. jcsd
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