k_air omega_acpr/cs_air Wave number (rad/m) a0 i*omega_acpr*v0 Piston acceleration (m/s^2) z0 P/v0 Piston impedance (ohm) eta0 z0/(rho_air*cs_air) Normalized piston impedance alpha0 real(atanh(eta0))/pi Hyperbolic piston impedance factor beta0 imag(atanh(eta0))/pi Hyperbolic piston impedance factor alphaL alpha0 Hyperbolic radiation impedance factor betaL beta0-k_air*L/pi Hyperbolic radiation impedance factor etaL tanh(pi*(alphaL+i*betaL)) Normalized radiation impedance zL nojac(etaL)*rho_air*cs_air Radiation impedance (ohm) alpha0_ana alphaL_ana(k_air*a) Hyp. piston imp. factor beta0_ana betaL_ana(k_air*a)+k_air*L/pi Hyp. piston imp. factor eta0_ana tanh(pi*(alpha0_ana+i*beta0_ana)) Normalized piston imp. z0_ana eta0_ana*rho_air*cs_air Piston impedance (ohm)