6. Acoustic transfer function of an isothermal line

The value of introducing the matrices or thermoacoustic transfer functions of a circuit's components is obvious when modeling for optimization. The theory developed above also makes it possible to characterize an isothermal component by its characteristic matrix M _di . Thus, for the case of isothermal walls, let B _T ≥ 0, neglecting thermal relaxation 1/r _T , and positing for acoustic admittance A _U ≥ jωc _u , with Δ ≥ – 4C _T ≥ 4Z _U A _U , we finally find the following matrix: