Seat-Dip Effect の基本的メカニズムに関する研究 : 平行な障壁の縮尺模型実験結果を用いた検討

概要

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The mechanism of seat-dip attenuation was examined using a simplified parallel barrier model representing rows of auditorium seats. From the results measured in the full-scale auditoria, seat-dip attenuation was thought to be caused by interference between the direct sound wave and the successive waves forming a negative-positive sequence in the impulse response immediately after the direct sound. The negative pressure wave was found to be caused by barrier (seat back) top diffraction and not to be reasonable to apply local reactive hypotheses. The measurement arrangements altering the geometry of the parallel barrier on the floor enabled to clarify the effect and cause of the positive wave. The diffraction at the barrier tops reflected off the floor, resulted in positive wave in the impulse response, caused the excessive attenuation at low frequencies interfering with the direct sound, and the arrival time of the positive wave determined the frequency of the maximum attenuation. The phase relationships depending on the diffraction angle were found to be crucial in order to explain the mechanism of the seat-dip attenuation, and these can not be explained by vertical resonance alone suggested by the previous study.
社団法人日本音響学会の論文