A study of sound field in a standing wave tube with flow and lateral Helmholtz resonator II. Experimental confirmation and results discussion

An experimental apparatus of a standing wave tube with flow and lateral Helmholtz resonator has been set up to verify the theoretical analysis presented by authors successfully, in which the discontinuity condition at the joint between the standing wave tube and Helmholtz resonator in the case of flow, the refection condition at the end of the standing wave tube and the acoustic impedance of Helmholtz resonator are included. Meanwhile the coefficients of end correct and equivalence radius have been obtained by experiments. Then several results from the theoretical analysis and experiments are used to discuss the effects of flow on the performance of Helmholtz resonator and the sound field in the standing wave tube. It is shown that using of Helmholtz resonator for the standing wave tube with flow is still a efficient method of noise reduction, even though because of flow the effect of noise reduction could be a little reduced.