A centrifugal fan includes a brushless d.c. motor, an impeller mounted on the motor and a scroll on which the motor is mounted. The scroll defines the air inlet and outlet and has an outer wall curved around the impeller to define a divergent air flow path. By truncating the scroll at the outlet substantially to eliminate any flat portions on the outer wall susceptible to mechanical vibrations at frequencies excited by the d.c. motor, a noise reduction is achieved. Further noise reduction may be achieved by resiliently mounting the motor on the scroll.
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