エンクロージャ円形開口部からの放射音の回折

抄録

This paper deals with the diffracted sound field around a rectangular enclosure theoretically and experimentally, which has one or two apertures and contains sound sources inside. The sound pressure level distribution in the diffracted sound field has been computed based on Pierce's approximate expressions for sound diffraction over a single wedge or a three-sided semi-infinite barrier with two edges, and actually measured with the sound visualizing device built as a trial. In the computation, it is assumed that the sound radiation from an aperture can be expressed by a point source or distributed ones according to lower or higher frequencies. Based on these results, the applicability of the approximate expressions is examined to the estimation of the diffracted sound field around actual enclosures. The results may be summarized as follows : (1) When the distances from each edge to adjacent edge, source and observation point are larger than one third wave length, the computed results by Pierce's approximate expressions are in sufficient agreement with the experimental results. (2) The complicated directional patterns of the diffracted sound field can be grasped sufficiently in detail by using the sound visualizing method.