Abstract
In recent years, with the rise of interest in environmental problems, noise reduction of motors is required. There are three kinds of motor acoustic noise: ventilation noise, electromagnetic noise and machine noise. Ventilation noise may be assumed to commonly consists of fan noise in high speed machines. Fan noise 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. Therefore, this paper describes space resonance frequencies and resonance mode of the fan channel analyzed by FEM and experiments. The effect of rotational sound and resonance mode on noise is described.
