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

  • #1

Homework Statement


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?



Homework Equations



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

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


The Attempt at a Solution


I think that Vsheet=0 since the pressure is not enough to move the sheet.
we dont know Pfront.
 

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