Efficient and broadband sound absorption properties of slotted aluminum foam

Abstract To enhance the sound absorption performance of aluminum foam, a slotted structure was developed. Firstly, the theoretical model of sound absorption for the slotted aluminum foam was established by the transfer matrix method. Secondly, the finite element model was established using COMSOL software to predict the sound absorption coefficient. The reliability of the theoretical and finite element models was validated through impedance tube experiments. The sound absorption mechanism is investigated by analyzing the internal sound field. Finally, the sound absorption properties of aluminum foam with other slot patterns are investigated. Additionally, the factors that influence sound absorption properties are investigated. The results indicate that the slots alter the sound pressure distribution within the material, inducing a pressure diffusion effect. When sound waves enter the interior of the material through the narrow slots, they are absorbed and dissipated by the matrix material on the sides of the slots. The sound absorption coefficient can be improved by increasing the thickness, slot scale, and slot depth of the slotted aluminum foam. Specifically, when the slot depth is 15 mm, and the slot width is 5 mm, the average sound absorption coefficient of incompletely slotted aluminum foam in the frequency range of 1000 ∼ 6300 Hz is 0.86, which can realize broadband sound absorption. With the increase of slot depth, the sound absorption peak becomes more pronounced.