The propagation of sound waves is described by partial differential equations for the acoustic pressure and the acoustic fluid velocity. The solution depends on the shape of the enclosure and on the boundary conditions. Among various methods for the discretization of partial differential equations, the multidimensional wave digital filter approach is known to yield robust algorithms for the dis...

The radiation of acoustic modes from an aeroengine intake duct is reviewed. The method is based upon a computational scheme which allows acoustic waves, propagating inside the intake duct of a generic aircraft engine, to be admitted into a computational domain that includes the duct section, the exit plane of the duct, and the surrounding flow. The method comprises three elements: a matching pr...

A method to compute the acoustic characteristics of a simplified three-dimensional vocal-tract model with asymmetric wall impedances is presented. The acoustic field is represented in terms of both plane waves and higher-order modes in tubes. This model is constructed using a connected structure of rectangular acoustic tubes, and can parametrically represent acoustic characteristics in higher f...

A Q-switched frequency Nd:YAG laser was focused on copper, aluminum, and lead targets. The acoustic emission accompanying plasma formation was acquired and analyzed in both the time and the frequency domains. Spectral analysis of the shock wave has proved to be a simple and low-cost diagnostic of plasma phenomena. In the time domain, several propagation mechanisms of the shock wave were observe...