Abstract
Aerodynamic noise generated from a high-speed train is a major environmental problem and its accurate estimation is essential for the efficient developments of the noise reduction technique. For the study of the aerodynamic noise, wind tunnel test with microphone array is useful to recognize noise sources easily. On the other hand, quantitative estimation will be also important for the further study. In order to evaluate the aerodynamic noise accurately, influence of the sound reflection due to the ground plate should be eliminated. In this study, we propose a method to correct a result of the microphone array measured with a sound reflection. First, acoustic interference caused by an image source was modeled suitably. Second, the reflection model was adapted to the beam forming analysis and the directive pattern, that is SPL distribution, was calculated. Finally, on the basis of the integrated SPL distribution, the correction coefficient was obtained. The method was also evaluated in the speaker test. It was shown that the correction level become large below approximately 2kHz and the source location near the ground, although the level in the higher frequency or higher source position are relatively small less than 1dB. It was also found that the integration area has an influence on the correction level especially in setting a threshold value.
