Modifications of a handheld vacuum cleaner for noise control

Sound power measurements were performed on a handheld vacuum cleaner in order to identify predominant noise generating mechanisms and recommend corrective noise control modifications that would result in no increase in production costs. These modifications were then implemented and their effectiveness quantified. The noise radiated by the vacuum cleaner was found to be dominated by aerodynamic sources with the tone at the blade passing frequency (BPF) of the vacuum working fan being the most annoying component. Modifications to the fan casing reduced this BPF tone up to 8 dB in level. A nine bladed vacuum working fan also reduced the BPF tone level 8 dB. A vacuum working fan with unevenly spaced blades and fan shroud modifications were introduced in an attempt to mask the fan BPF tone by creating additional tones. Jury survey results showed that the vacuum cleaner modified to create additional tones was preferred 3 to 1 over the baseline unit even though the overall tone loudness level was increased by 6 dB.