Abstract:
Transportation noise sources are usually in motion. Previous analyses have simplified the problem by assuming a moving source either as a quasistationary point source or, in the case of traffic noise as a continuous line source problem. This assumption is valid for a vehicle traveling at low speed but is unlikely to be adequate for a source traveling at a non-negligible Mach number. A notable example is a high-speed train traveling in excess of 200 km h[sup -1]. In this paper, as a first approximation, the high-speed train is modeled as a moving monopole source above an impedance ground. Although the sound field due to a moving monopole source in an unbounded medium is well known, there is relatively little attention focused on a moving point source near to an impedance ground surface. Asymptotic analysis has been conducted to derive a closed-form analytic solution. The project described in this paper is a canonical problem. The solution (Green's function) will be a building block for modeling noise propagation due to high-speed trains in future studies which includes, for example, a moving line source and a moving dipole, etc. [Work supported by EPSRC, UK.]