Tonal and broadband noise control of an axial-flow fan with metal foams: Design and experimental validation

This paper presents an application of metal foams for controlling aerodynamic noise of an axial-flow fan. A configuration of a semi-open cell metal foam combined with a backing cavity is employed to attenuate the tonal component while an open-cell metal foam is used to absorb the broadband component. An acoustic impedance model is employed to determine the optimal geometrical parameters of the metal foam and the cavity. Experimental results confirmed that the tonal noise is greatly reduced by the semi-open cell metal foam and the open cell metal foam shows a potential of absorbing the broadband noise.