Experimental evaluation of characteristics for high-speed moving source

In this study, we evaluate the characteristics of a moving sound source in frequency and amplitude by visualizing a sound field around it. This is because train noise propagates with the characteristics of a moving sound source. To evaluate the characteristics, the visualization measurement was conducted using an optical sound measurement system, parallel phase-shifting interferometer, and low-noise moving model test facility. In the frequency result, modulation was observed, and the frequencies agreed well with the theoretical values. To evaluate the amplitude of sound, we determined the correction coefficient by which the integral pressure fluctuations recorded with the parallel phase-shifting interferometer are converted to the ones in one cross-section. By applying the conversion coefficient to the measured sound field, the shadow zone generated by the boundary layer was observed.