摘要:
在普通的声学材料中，质量密度通常是一个实数。能量耗散是由材料的形状或体积变化引起的，这与复数模量的虚部有关。这里，我们利用声学超材料也可以实现复数的动态质量密度。在这种情况下，能量损耗是由材料的动量变化引起的。我们分析了这种复数的动态质量密度的物理成因，并提出了计算这种有损耗的声学超材料的复数动态质量密度的理论方法。得到的有效复数质量密度通过有限元模拟进行了验证，包括传输研究和实现相干完美吸收。我们的工作展示了一种实现复数质量密度的方法，这找提高声波的吸收上有重要的应用。
Abstract:
The mass density of normal acoustic materials is usually a real number. Energy dissipation is in-duced by the volume or shape change of the materials, which relates to the imaginary parts of complex moduli. Here, we show that by using acoustic metamaterials, complex dynamic mass density can also be realized. In this case, energy dissipation is induced by the change of momentum of the material. We analyze the physical origin of such complex mass density and provide a theoretical approach to calculate the effective complex dynamic mass density for acoustic metamaterials with dissipation. The obtained effective complex mass density is verified by finite element simulations, including both transmission studies and realization of coherent perfect absorption. Our work shows a way to realize complex mass density, which has important applications in enhancing absorption of acoustic waves.