Studies on the Measures for Prevention of Noise on Chute Used Block Roughness

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This study investigated the measures against noise generated by flow of drops or chutes, based on the case study of noise generation in irrigational canals. And also noise characteristics, such as the scoustic power level (PWL), the A-weighted sound level (L(A)) in a hydraulic-jump-type and water-cushion-type drops were studied in fields.The results of this study are summarized as follows :1. As a preventive measure of that noise, a hydraulic model test was performed experimentally with chute used block roughness and the chute with block roughness was applied to the field based on the hydraulic model. The results of this experiment suggest that this method of energy-dissipation be effective as a measures for noise prevention.2. It was found that both the scoustic power level and the A-weighted sound level increase linearly with the inflow energe of hydraulic-jump and the drop of energe per unit width canal. And, both the hydraulic-junmp-type and the water-cushion-type drops, the ratio of diminishment of A-weighted sound level in the traverse direction drops tends to be higher than that in either downstream or upstrieam direction