Ray-tracing semiclassical (RTS) low frequency acoustic modeling validated for local and extended reaction boundaries

The recently introduced acoustic ray-tracing semiclassical (RTS) method is validated for a set of practically relevant boundary conditions. RTS is a frequency domain phased geometrical acoustics method which directly reproduces the acoustic Green's function. As previously demonstrated for a rectangular room and weakly absorbing boundaries with a real and frequency-independent impedance, RTS is capable of modeling also the lowest modes of such a room, which makes it a useful method for low-frequency sound field modeling in enclosures. In practice, rooms are bounded with diverse types of materials, resulting in a frequency-dependent, phase-modifying absorption/reflection. In a realistic setting, we test the RTS method with two additional boundary conditions: a local-reaction boundary simulating a resonating absorber and an extended-reaction boundary representing a porous layer backed by a rigid boundary described within the Delany-Bazley-Miki model, as well as a combination thereof. The RTS-modeled spatially dependent pressure response, frequency-band decay curves and reverberation times are compared to those obtained by the finite element method. The RTS results show systematic agreement for all boundary conditions and disclose some interesting particularities of the method.