Effect of Pipe Length Immersed under Water Surface on the Tone Radiated from a Resonant Pipe

摘要

The intrinsically peaceful sound of water musical instrument depends on the air-bubbles formed by the impact of the water droplets on the water surface. Thus the control of the air-bubbles is the key to the tonal quality. The pipe length sunk in the water determines the quality of the sound source by affecting the shapes of the air-bubbles. The purpose of this research is to study the effect of a pipe length immersed under water surface on the tone of a resonant pipe. Experiments have been carried out through the simultaneous measurement of both the generated sound and the formation of air bubbles. A water jet spouted from the nozzle changes instantaneously into many water droplets within a distance of about 20cm from the nozzle exit. The dominant sound at the exit of the resonated pipe is produced by the vibration of the air-bubbles and by the resonance of air-column in the pipe. If the pipe length is immersed deeper in the water, the column of air-bubble becomes longer and its vibration is generated later. Moreover, when the pipe length is immersed deeper under water surface, the dominant frequency of the sound source based on the bubble vibration is shifted to the lower frequency.