$4\mathrm{.}2$ Absorbing Layer

Please determine the sound absorption coefficient for normal incidence for a $10cm$ thick porous layer in front of a sonically hard wall. The porous material has an air flow resistivity of $10kN\frac{s}{m^4}$ and a porosity and tortuosity ~~$1.$ The fluid is air. Calculate the values for $200Hz$ and $2kHz.$

Note: Use the model of Hamet.