The experimental research on the acoustical property of the Japanese Bell subjected to local paring is presented in order to find the method of adjusting the frequency of the beat. It has been made clear that the natural frequency is advanced slowly by paring the nipples, and the natural frequency is reduced by paring locally the surface of bell. When the paring is applied to the L nodal line of the fundamental tone, the H frequency varies larger than the L one. Accordingly, the beat frequency, that is, the difference between the H and L frequency, can be adjusted.
In this paper, acoustic interferences in periodic vortex-shedding from a circular cylinder in an air flow are investigated with the aid of constant temperature hot-wire anemometers, a frequency analyzer and so on. In this way, we investigated the mechanism of vortex-shedding. Experiments were made at Reynolds numbers of 1800 and 5600, and sounds for each Reynolds number were progressive and standing sound fields, respectively. As the result of the acoustic interferences, the vortices are shedded nearer the cylinder, and are stronger than these without sounds. ; however, the shedding frequency changes a little. There are two acoustic frequency groups which produce powerful effects on vortex-shedding. One is a narrow frequency range centering around the natural vortex-shedding frequency, and the other is a relatively wide frequency range which corresponds to the frequency of the laminar-turbulent transition wave in the separated boundary layers. The latter has a larger effect on the vortex-shedding than the former.