抄録
The small type high rotating speed water pumps which have inverter for rotating speed control have been served and are more quiet than those which install flow control valve. However, some annoying flow noise are closed up as the ordinal pumps noise have become quiet. This annoying noise source and generation mechanism have been experimentally studied. It was made clear by this study that the diffuser flow generated separated flow and radiated the annoying noise. The improved pump with smoothed diffuser decrease the annoying noise although noise spectra do not remarkably change. The analysis of sound quality with respect to this pumps noise have been examined and It has been recognized that "Loudness level" and "Sharpness" are remarkably decreased. It is concluded that the reduction of separated flow on the diffuser induced the decrease of "Loudness level" and "Sharpness" with respect to noise from the high speed pumps.
