Abstract
In recent years, with the rise of interest in environmental problems, noise reduction in motors has come to be stringently required. There are three kinds of motor acoustic noise: I ventilation noise, II electromagnetic noise and III machine noise. It is assumed that ventilation noise mostly consists of fan noise in high speed machines. As to fan noise, this is produced by the number of rotations and the number of fan blades and by the turbulence sound produced by the disturbed flow of cooling air. Regarding fan blade sound and turbulence sound, many studies on noise reduction have been done by flow analysis using examination of fan blade number and shape. However, papers describing the space resonance frequency of the fan space that is a propagation channel of the fan noise have not been found. Thus, in this paper, space resonance frequency and resonance mode of the fan channel was analyzed by FEM and experiments. These have not yet been studied by research to the present. In addition, the effect of rotational sound and resonance mode on noise is described.
