In this study, we prepared metal hollow sphere composites (MHSCs) using metal hollow spheres (MHSs) by pressure casting under vacuum conditions, and investigated the acoustic properties. The density of the MHSCs was measured using the mass to volume ratio, the microstructure of the MHSCs was observed using a scanning electron microscope, and the acoustic properties of the MHSCs were tested using an impedance tube. The measured MHSCs showed that the densities of the MHSCs with the random distribution of MHSs with diameter ~3.28 mm (1.74 g/cm³ to 1.77 g/cm³) (MHSC-3.28) were nearly equal to that of the MHSCs with the random distribution of MHSs with diameter ~5.76 mm (1.74 g/cm³ to 1.76 g/cm³) (MHSC-5.76), and lower than that of the MHSCs with the layered structure of MHSs with diameter ~3.28 mm (1.93 g/cm³ to 1.97 g/cm³) (MHSC-LS). Microstructural observations confirmed that the interface region between the MHSs and matrix demonstrated a simple physical combination pattern with pores. The acoustic properties of the MHSCs showed that the sound absorption coefficient of MHSC-LS was lower than that of MHSC-3.28 and higher than that of MHSC-5.76 at off-resonance. The sound absorption coefficient peak value of MHSC-3.28 was higher than that of MHSC-LS, and lower than that of MHSC-5.76 at resonance. The sound transmission loss of MHSC-3.28 was lower than that of MHSC-5.76, which shows the rules are independent from the resonance. The sound transmission loss of MHSC-LS was higher than that of MHSC-5.76 at resonance, but lower than that of MHSC-3.28 at off-resonance. In addition, we discuss the propagation mechanism of the sound waves in the MHSC, which is mainly determined by the distribution of the MHSs in the MHSC.

中文翻译：

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压铸法制备316L不锈钢空心球复合材料的声学性能

在这项研究中，我们通过在真空条件下压铸制备了使用金属空心球（MHS）的金属空心球复合材料（MHSC），并研究了其声学性能。使用质量/体积比测量MHSC的密度，使用扫描电子显微镜观察MHSC的微观结构，并且使用阻抗管测试MHSC的声学特性。测得的MHSC的密度表明，直径为〜3.28 mm（1.74 g / cm ³至1.77 g / cm ³）的MHS随机分布的MHSC的密度（MHSC-3.28）几乎与随机分布的MHSC的密度相同。直径〜5.76 mm（1.74 g / cm ³至1.76 g / cm ³）（MHSC-5.76），并低于直径约3.28 mm（1.93 g / cm ³至1.97 g / cm ³的MHS分层结构的MHSC））（MHSC-LS）。微观结构观察证实，MHS和基质之间的界面区域显示出具有孔的简单物理组合模式。MHSC的声学特性表明，MHSC-LS的吸声系数在偏共振下低于MHSC-3.28，但高于MHSC-5.76。MHSC-3.28的吸声系数峰值在共振时高于MHSC-LS，但低于MHSC-5.76。MHSC-3.28的声音传输损失低于MHSC-5.76，这表明规则与共振无关。MHSC-LS的声传输损耗在共振时高于MHSC-5.76，但在非共振时低于MHSC-3.28。另外，我们讨论了声波在MHSC中的传播机制，