kx_e sin(theta0) Plane wave direction, x
ky_e -cos(theta0) Plane wave direction, y
k0 intop_pnt(acpr.k) Free-field wave number
kx k0*kx_e Background plane wave, k_x
ky k0*ky_e Background plane wave, k_y
Zn aveop_bnd(acpr.p_t/(nx*up(acpr.vx)+ny*up(acpr.vy)))/intop_pnt(acpr.rho*acpr.c) Specific surface impedance normalized
Pin intop_bnd(-acpr.I_by) Incident power
Pout intop_bnd(acpr.I_sy) Outgoing power
alpha 1-Pout/Pin Absorption coefficient