1989 年 55 巻 1 号 p. 117-122
An approximate expression for multiple-edge diffraction of sound around a polygonal pillar can be derived based on Pierce's asymptotic solution for sound diffraction around a wedge barrier The effect of multiple-diffracted waves around a rectangular pillar is clarified by calculating the distribution of sound pressure levels for each diffracted wave using the approximate expression. On the basis of the results for each diffracted wave, a practical calculation method of multiple-edge diffraction sound field around a rectangular pillar is proposed. This method is applied to the calculation of the sound field around a rectangular pillar which is produced by a spherical sound wave incident on its side. The calculated results are compared with the experimental ones. In the experiment, a sound visualization technique using three color-light-emitting diodes is used to measure the distribution of sound pressure levels around rectangular pillar models in detail. The calculated results agree well with the visualized ones. All these results show that this calculation method is of practical use.