No abstract

Metal foams are interesting as sound absorbers because of their strength, low mass, high hardness, and damping. To foam fabrication more accurate and achieve higher sound absorption coefficient (SAC), the effective parameters should be optimized. In earlier study (DOI: 10.32604/sv.2021.09729), the parameters of porosity percent- age (Ω), pore size (D) and pore opening size (d) were optimized by the authors. In this study, we intend to investigate the effect of optimized Ω percentage, D size and d size on the SAC of aluminum foam in the frequency 0 to 8000 Hz with the thicknesses of 5, 10, 20, and 30 mm. The genetic algorithm was performed employing the Lu model, using MATLAB software. According to the results, the optimum values of Ω, D, and d at different frequencies and thicknesses are not constant. That is, at any given thickness and frequency, there are specific optimum amounts. This study provides a way to improve the SAC performance of porous metal materials for various and targeted applications.

Due to its unique features, the metal foam is considered as one of the newest acoustic absorbents. It is a navel approach determining the structural properties of sound absorbent to predict its acoustical behavior. Unfortunately, direct measurements of these parameters are often difficult. Currently, there have been acoustic models showing the relationship between absorbent morphology and sound absorption coefficient (SAC). By optimizing the effective parameters on the SAC, the maximum SAC at each frequency can be obtained. In this study, using the Benchmarking method, the model presented by Lu was validated in MATLAB coding software. Then, the local search algorithm (LSA) method was used to optimize the metal foam morphology parameters. The optimized parameters had three factors, including porosity, pore size, and metal foam pore opening size. The optimization was applied to a broad band of frequency ranging from 500 to 8000 Hz. The predicted values were in accordance with benchmark data resulted from Lu model. The optimal range of the parameters including porosity of 50 to 95%, pore size of 0.09 to 4.55 mm, and pore opening size of 0.06 to 0.4 mm were applied to obtain the highest SAC for the frequency range of 500 to 800 Hz. The optimal amount of pore opening size was 0.1 mm in most frequencies to have the highest SAC. It was concluded that the proposed method of the LSA could optimize the parameters affecting the SAC according to the Lu model. The presented method can be a reliable guide for optimizing microstructure parameters of metal foam to increase the SAC at any frequency and can be used to make optimized metal foam.