The 22nd International Congress on Sound and Vibration location:Florence, Italy date:12-16 July 2015
Geometrical acoustics (GA) is well-suited for interior acoustics problems at high frequencies when the boundaries are described by absorption coefficients. If the boundaries are described by an impedance, mid-frequency problems can also be solved if a phase factor, which is dependent on the total distance a ray has traveled, and a complex-valued plane wave reflection coefficient are included. However, including velocity boundary conditions in the context of GA is not as straightforward. One existing method approximates a vibrating panel as a distribution of acoustic monopoles. Another, the Green Ray Integral Method (GRIM) solves a boundary integral in which the pressure on the surface is determined by a ray tracing procedure. However, in both cases, it is assumed that the acoustic fluid does not influence the velocity field of the vibrating structure. These problems are best solved using other methods, such as the finite and boundary element methods for low frequencies and statistical energy analysis (SEA) for high frequencies. An alternative approach is presented here for coupled (vibro-)acoustic problems at mid- to high frequencies using geometrical acoustics and the patch transfer function (PTF) method. The PTF method is a general sub-structuring procedure in which a common surface between two domains is divided into patches and the spatially averaged pressure and normal velocity over each patch are conserved. The calculation of patch transfer functions of an acoustic domain using geometrical acoustics is detailed, and the approach is applied to a strong coupling case by dividing an acoustic volume into two separate volumes. In this way, convergence criteria and accuracy of the approach are quantified.