| 摘要 |
<p>In an appliance, such as a cyclonic vacuum cleaner (1), a motor is arranged to drive an impeller fan located in a motor and fan unit (3). The rotation of the impeller may cause nuisance tones to be generated. A silencing arrangement is provided to control such noise and comprises a plurality of discrete passive silencers in the form of tube silencers (23) arranged in a first set (18) and a second set (24). The tube silencers (23) have open end portions arranged to face the fan and the silencers of the first set (18) are spaced from the silencers of the second set (24) in both axial and radial directions. This combination gives the same effect as an array of closely spaced tube silencers - however, by spacing the silencers in two directions, fluid is allowed to flow freely.</p> |
