To secure an air passage in a tunnel-like discharge channel, and at the same time to reduce propagation of noise of a waterwheel in the tunnel-like discharge channel.
The tunnel-like discharge channel 20 for discharging water 21 used for rotating the waterwheel 10 arranged in a waterwheel housing 13, is connected to the waterwheel housing 13, and a noise reducing apparatus 25 in the tunnel-like discharge channel 20, which has the air passage 23 formed over a water surface 22 in the tunnel-like discharge channel 20, is provided with two first rubber curtains 30 and two second rubber curtains 40. Specifically the air passage 23 is formed in a gap between a lower edge 31 of the first rubber curtain 30 and the water surface 22 and a space above an upper edge 41 of the second rubber curtain 40 in the tunnel-like discharge channel 20. Then the location of the lower edge 31 of the first rubber curtain 30 is set lower than the location of the upper edge 41 of the second rubber curtain 40, and therefore propagation of noise in the air passage 23 in the tunnel-like discharge channel 20 is reduced.
COPYRIGHT: (C)2008,JPO&INPIT
Yasutaka Miura
Tominaga Hirofumi
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