1992 Volume 35 Issue 4 Pages 623-632
One specific feature of the aerodynamic sound produced at the face end region is that the radiation becomes equally weak by filling root spaces as by shortening the center distance. However, one can easily expect that such actions make the air flow faster, and consequently make the sound louder. This paperattempts to reveal the reason for such a feature. First, air flow induced by thepumping action of the gear pair was analyzed regarding a series of root spaces as volume varying cavities which have channels to adjacent cavities as well as the exit/inlet at the face ends. The numefical analysis was verified by the hot wire anemometer measurement. Next, from the obtained flow response, the sound source was estimated to be a combination of symmetrically distributed simple sources. Taking the effect of either the center distance or root filling into consideration, it became clear that the simplified model can explain such a feature rationally.