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.