Acoustical properties of the falling water sound according to differences in the downstream slope angle of a single weir
2006
Gotoh, M.(National Inst. for Rural Engineering, Tsukuba, Ibaraki (Japan)) | Kobayashi, H. | Namihira, A. | Tsunesumi, N.
As a result of urbanization and the appearance of mixed land use, the falling water sound from head works and ground sill works etc. has become an environmental problem. The acoustical properties of the falling water sound at diversion weirs with downstream slope angles of 90 deg and 30 deg were studied by hydraulic tests using a real scale model. The results of the tests revealed the following facts: 1) in comparison with a falling water flow (90 deg), the G property value and the A property value in the case of a slope water flow(30 deg) is decreased, downstream slope angles of 30 deg is effective as a measure against the falling water sound; 2) in the case of a falling water flow (90 deg), the sound pressure level at a frequency at or above 3Hz is higher than that of a slope water flow, and the sound pressure level tends to be dominant, particularly near 10Hz; 3) the conversion rate of the energy of the flow of a falling water flow to low frequency sound energy is approximately 6 x 10(-6) times, and in the case of a slope water flow, this conversion rate is about 1/30 times lower at approximately 2 x 10(-7).
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