Low frequency sound insulation performance of membrane-type acoustic metamaterial with eccentric mass block

Abstract To improve the sound insulation performance in the low frequency band of membrane-type acoustic metamaterial (MAM), membrane-type acoustic metamaterial with eccentric mass block (MAMEM) is used as the object in this paper. The influence of composite mass block on the low frequency sound insulation performance of MAMEM is also studied. Firstly, a mathematical model of sound insulation based on MAMEM was conducted. Secondly, the elastic layer is introduced into the mass block of the MAMEM to form a membrane-type acoustic metamaterial with eccentric composite mass block (MAMECM) structure. The study shows that the peak sound insulation frequency of the structure is obtained with a left shift of 70 Hz, and the introduction of the elastic layer will be beneficial to realize the low frequency regulation of the structural band gap. Thirdly, the influence of the thickness of the elastic and metal layers on the sound insulation of the MAMECM was discussed. The study shows that when the thickness of the metal layer is 1 mm and the thickness of the elastic layer is 10.7 mm, the peak sound insulation reaches 70 dB at this frequency. The peak frequency of sound insulation can reach 260 Hz, which is 140 Hz lower than the MAM at the same mass. Moreover, under the premise that the total mass of composite material blocks remains unchanged, the sound insulation peak frequency of sound transmission loss (STL) curve will shift to the left when the thickness of metal layer is smaller, and the sound insulation at the peak frequency is larger. Finally, the accuracy of the results is verified by experiments.