With increasing customer expectation for silent operation of home appliances and electrical devices, much effort has been put into reducing the noise level in the design and the development stages. This study presents some preliminary procedures for use in designing the optimal shapes of the cross-flow fan system that is widely used in the indoor unit of split type room air-conditioners. In this study some experiments have been carried out to investigate influences of the various shapes of the fan blades, scrolls, and stabilizers on the performance and noise characteristics of the fan. Experimental results show that the specific noise level is closely related to the performance characteristics and is dependent on the efficiency of the fan. Acoustical analysis of the sound spectra of the cross-flow fan has also been performed to describe the relationship between the sound pressure level and fan performance. In the low efficiency region, the noise level is increased due to the flow fluctuations in the frequency region where the Strouhal number is around or less than 1.
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