Noise propagation and attenuation in L-shape duct with flow

Clarifying duct noise is gathering attention for various industries. Duct noise is one of the noise problems in the equipment such as air conditioner and ventilation system. In the duct noise, the noise generated by the sources due to the fan or motor are included, and these noise propagate in the L-shape duct with flow. However the propagation mechanism of these noise are not clarified, especially in the case of the propagation in the duct with flow. In this paper, we investigated the propagation and attenuation of the noise generated by the speaker in the duct with or without a flow both experimentally and numerically. The results show that in the case of the duct with the flow, the noise generated by the speaker at frequency more than 1200 Hz are damped more than in the case of the duct without the flow.In the numerical simulations, the results shows that the strength of the noise sources on the duct wall decreases in the case of the duct with a flow more than in the case of the duct without a flow. In the numerical simulations, we applied the coupling method using CFD and acoustic BEM solvers.