Frequency-response characteristics of interaction tone noise radiated from a centrifugal compressor with vaned diffuser are discussed by experiments and also by noise transmission model. The interaction tone noise is supposed to be caused by the periodic pressure fluctuation in the vicinity of the leading edge of diffuser vanes, and to show the characteristics of dipole noise source, noise source characteristics in an ideal sense should increase in the 6th power against the flow velocity. Then the level discrepancy between the noise source and measured sound pressure level is considered to be affected simply by the frequency-response characteristics of the noise transmission passage which are predicted by introducing a one-dimensional linear wave model. In the model, leading edge of the diffuser vane is considered to be a noise source, and sound wave travels through the passages of main and splitter blades in the impeller, inducer and inlet duct as a plane wave. The modeled data is found satisfactorily to predict the response characteristics of the noise transmission passage. The noise source characteristics are also discussed by precise measurements of pressure fluctuation level within impeller passages.

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