A Study of Broad Band Noise Generated form a Multi-Blade Sirocco Fan

The basic characteristics of the broad band noise (BBN) generated from a multi-blade sirocco fan are summarized. As a basic experiment of the BBN, the noise characteristics generated from an arc blade were researched in the wind tunnel experiment, and the distributions of the sound sources of the same blade were visualized by a numerical computation. As the sound sources generating at the separation point moved to trailing edge, the scale of the sound sources became large. Moreover, the sound sources were not necessarily uniform scale. The sound pressure generated from the multi-blade sirocco fan was proportional to third power of the flow coefficient, and the BBN in the spectrum distribution was in inverse proportion to third power of the frequency. This tendency of the noise of the fan was same as the noise characteristics of the are blade. In the fan noise of the multi-blade sirocco fan, the influence of the BBN appeared in the flow rate vicinity of the maximum efficiency point