The blade-passing frequency noise, abbreviated to BPF noise, of a low-specific-speed centrifugal blower could dominate the overall noise level, if sufficient care is not taken. Therefore, many blower noise investigations have been focused their attention on the reduction and the prediction of the BPF noise level [1]-[3]. Since the BPF noise depends not only on the frequency-response characteristics of the noise transmission passage but also on the strength of the noise source, the authors made an experimental evaluation of both contributions in previous investigations [4],[5]. The effect of noise transmission passage was estimated by introducing a one-dimensional plane-wave model, and the predicted noise level agreed well with experimental results. While the strength of the noise source was evaluated using a correlation analysis, and the distribution of the effective noise source extent on the scroll surface was experimentally determined.
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