Case study: An appraisal of wet/dry vacuum noise

An investigation was conducted to analyze the difference in sound between a high end wet/dry vacuum and a consumer version to determine what design features make the high end model more effective at controlling noise emissions. As a first step, the sound power level for each vacuum was measured and the higher end vacuum was determined to be 7 dB quieter. To gain further insight, the sound power for the high end model was measured with and without the foam in the exhaust. As anticipated, the higher end model was quieter at higher frequencies due to the absorbing material in its exhaust pathway. A crude sound quality assessment was then conducted. The jury appeared to be sensitive to the high frequency sound, and it was concluded that the absorption of the foam in the high end model significantly reduces sound power, and that the convoluted flow path and the direction of flow help to reduce noise levels for the operator.