STRUCTURE-BORNE NOISE GENERATED BY VACUUM CLEANER SUCTION UNITS

摘要

Noise emitted by a vacuum cleaner suction unit consists of airborne and structure-borne noise. The airborne noise is generated mainly by the turbo blower and the structure-borne noise is generated mainly by the driving electric motor. Structure-borne noise is an audible sound that is structural in origin, i.e., it begins as vibration. Basically, each substructure of a suction unit has one of the resonance frequencies and can affect the overall vibration behaviour. The normal mode of vibration of each part of the suction unit depends on its mechanical properties. The structure-borne noise depends on the suction unit design and on operating conditions. In this paper the effects of vibrations of the suction unit structure on the noise characteristics have been measured and analysed at the design and off-design operation. Measurement results have shown that contribution of structure-borne noise to the total sound pressure level becomes important at partial flow rates, especially when the rotating stall and surge in the turbo blower appear, and is relatively less important at higher flow rates and towards the free delivery. Among geometrical parameters, the stator of the turbo blower and electric motor, or metal shield if any, are main origins of the structure-borne noise. A vaned diffuser built-in the blower has the greatest effect on the structure-borne noise.