Alleviation of Super Low Frequency Noise Generated by a High-speed Train Passing thorough a Tunnel

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(1) To accomplish the railway tunnel simulator, a fast opening gate valve was developed. The formation of the compression wave in a simulator are reproduced with a good quality.(2) Three-dimensional numerical analysis was developed on an impulse sound emitted from an exit of high-speed railway tunnel.(3) The effects of expansion chambers for super low frequency noise are investigated numerically and experimentally.(4) The higher mode waves on the reflected expansion wave and the emitted impulse sound develops due to the reflecting process of a pressure wave at the tunnel exit.(5) The directivity of impulse sound changes when the emitted solid angle decreases. Therefore, the change of magnitude of impulse sound is small when the emitted angle is larger than 45 degrees.(6) Optimum location of exit expansion chambers are found and the noise directivity have been clarifed.