Efficient prediction methods for the micro-pressure wave from a high-speed train entering a tunnel using the Kirchhoff formulation

The compression wave generated by a high-speed train emerging from the exit portal of a tunnel gives rise to an impulsive noise called a micro-pressure wave. In this study, new methods for the prediction of sonic-boom noise are proposed. The first method combines acoustic monopole analysis and the method of characteristics with the Kirchhoff method. The compression wave from a train entering a tunnel is calculated by an approximate compact Green's function, and the resultant noise at the tunnel exit is predicted by a linear Kirchhoff formulation. The second method couples the Kirchhoff formulation with the Euler equation, which is solved numerically for the generation and propagation of the compression wave. Numerical prediction of the compression wave, the propagation in the tunnel, and the micro-pressure wave obtained by the present methods are compared with measured data. The numerical results exhibit a reasonable agreement with the experimental data. The proposed methods in this study are shown to be very useful design tools for the nose shape of trains and the geometry of tunnels, and they can be utilized to minimize the pressure fluctuation in the tunnel and the corresponding booming noise. (C) 2001 Acoustical Society of America.