Abstract
The sound characteristics of the flow was investigated for some existing water-cushion type drops, the acoustic sound power level (PWL), A-weighted sound pressure level (L (A)) and the attenuation characteristics of the flow sound in the hydraulic phenomena of the drop flow were examined. The investigation showed as follows;(1) the PWL of the drops measured ranged between 86.6 dB and 104.7 dB, and was greater for drops with greater energy. The PWL and L (A) of the water-cushion type drops were investigated in terms of their energy, expressed as the following different hydraulic factors: discharge, water channel width, drop height (the difference in water level between the upstream drop point and the stilling basin), and the stilling basin depth at the drop point.(2) The PWL and L (A) generated at the drop could be estimated if the hydraulic factors from the relational diagrams for drop energy, PWL and L (A) are known.(3) Judging from its distribution characteristics, the transmission of flow sound in the upstream direction was small, which served as a guide to determining the position of the drop relative to residential areas where the flow sound may cause problems with noise.
