ノズルから吹き込まれる気泡が発する放射音の計測

摘要

水面に石を投げ込んだときや，コップに入った水にスト ローで息を吹き込んだとき，音が発生する.これらの音は， 気液界面での急激な圧力変動によって放出されるものである. このような生成音のなかでも，特に，液体中で気泡が軸対象 な変形することによる音響特性については，Longuet-Higgins によって理論的に検討されている.%Air bubble released from an underwater single-hole nozzle emits an acoustic sound. This paper aims to experimentally measure such an acoustic signal, simultaneously taken with a high-speed photography during the bubble detaching at the nozzle. At the instance of the bubble detachment the acoustic signal is observed to rapidly increase and, then, oscillatory decrease due to the oscillation of the conical surface at the tail of the bubble. The sound generated by an air bubble from the nozzle is found to be emitted just after the bubble detachment, and the resultant frequencies are measured to be two values of 280 [Hz] and 1400 [Hz], simultaneously.