Traditional double-panel structure has good sound insulation performance at middle to high frequencies, but it is difficult to achieve high sound transmission loss (STL) in low frequency range due to the mass law and mass-air-mass resonance. In this paper, a specially designed acoustic metamaterial layer is introduced to double panel systems to improve the low frequency sound insulation performance. A dynamic equivalent medium model for the acoustic metamaterial layer was presented, and then an analytical model for prediction of the STL of the double panel systems with acoustic metamaterial is developed based on the transfer matrix method. Theoretical results show that the low-frequency sound insulation performance of a double panel system can be significantly improved by introducing the acoustic metamaterial layer. The influence of system design parameters on the STL characteristics of the double panel system is analyzed. Furthermore, it is found that by properly placing porous materials in the double panel system, the low frequency sound insulation performance can be further improved. Since the proposed double-panel systems with acoustic metamaterials are simple and light-weight, they are convenient for large-scale manufacturing and engineering application, and thus have a broad application prospect in cabin noise reduction for aircrafts, ships etc.

Acoustic metamaterials; Double panel system; Low frequency sound insulation; Cabin noise reduction