Sound Insulation Properties of Truss-based Inertial Amplification Double-panel Acoustic Metamaterial

In recent years, a wide variety of periodic structures have come to the fore in the requirements for innovative noise and vibration solutions which are lightweight and compact. The vibro-acoustic properties of these structures are mostly analyzed by means of sound transmission loss (STL) calculations. To improve the STL of such lightweight structures, especially sandwich structures, without greatly increasing the structural complexity and the total mass, a truss-based inertial amplification double-panel acoustic metamaterial is presented. A truss structure consists of two lumped masses and four rigidly massless bars connected by moment-free hinges. The truss-based double-panel metamaterial and the cavity inside it form a panel-cavity-panel vibro-acoustic system. For the sake of the efficient STL calculations, a semi-analytical method based on the energy generalized variational principle is promoted, which can obtain the vibro-acoustic characteristics of the acoustic metamaterial-acoustic cavity coupling system as well. The displacement of the panels and the sound pressure of cavity are expressed as Chebyshev orthogonal polynomials. The feasibility of the developed method for efficient STL prediction is verified by comparing with the conventional finite element method. On this basis, numerical results clearly show that compared with the original panel-cavity-panel system, the inertial amplification acoustic meta-material exhibits a remarkable sound insulation performance within a low-frequency range which induced by the additional truss structures. Finally, parametric studies of inertial amplification angle and the depth of the cavity are conducted to reveal the variations of sound insulation performance. These parametric studies provide a guideline for tuning the STL peaks of the double-panel acoustic metamaterial.