近距離場音響ホログラフィによる円筒の構造インテンシティ計測及びリブの音響エネルギー流への影響について

概要

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A measurement method of structural intensity was proposed by developing the signal processing in near-field acoustical holography (NAH) in our previous paper [Jpn. J. Appl. Phys., 35, 3167-3174 (1996)]. The present paper extends that method to the structural intensity measurement in cylindrical geometry. Two samples used in the experiment are SUS304 cylindrical shells. One of them has a rib and the other has no rib. The experimental data are obtained and reconstructed over the frequency range between about 300 and about 3,000 Hz. The data at 488 Hz and 1,877 Hz are selected for specific and detailed investigation of structural intensity distribution, where 488 Hz lies in a pass band and 1,877 Hz in a stop band of the ribbed shell. According to the discussion of experimental results, it may be understood that the attached rib acts as a "light beam" at a pass-band frequency 488 Hz and a part of the intensity flow is reflected at and the rest is transmitted through the rib. However, the rib almost completely reflects the intensity flow by acting as a "heavy beam" when the driving frequency is a stop-band frequency 1,877 Hz. The overall mode cell structure is thus largely influenced by the action of a rib except for locally induced vortexlike structure. Also, the calculation of the power injected to the shell successfully leads to the identification and localization of the vibration source.
社団法人日本音響学会の論文