A tunable metamaterial muffler with a membrane structure based on Helmholtz cavities

摘要

With the recent advances in acoustic metamaterial science, the possibility of sound attenuation using Helmholtz cavity structures while reducing low-frequency noise has been demonstrated. However, the ongoing challenge addressed herein is the fact that among Helmholtz cavity structures to date, the silencing frequency is fixed in the traditional muffler. It is very inflexible in practical applications. To address this challenge, we first proposed a muffler with a membrane structure and multi-Helmholtz cavities. By simplifying the structure into a mass-spring model, we derived the negative mass density of a varying number of membranes. Next, we calculated the transmission loss (TL) through simulation using COMSOL software. The results of our analysis confirmed that the muffler can reduce noise when the mass density is negative, and the silencing frequency can be tuned by changing the number of membranes. The proposed adjustable muffler was validated experimentally, demonstrating a reduction in the transmission loss over 20 dB. This multi-cavity and multi-membrane metamaterial design enables the silencing frequency to be controlled based on the number of membranes, which may be used in applications in which the silencing frequency needs to be adjusted based on different environments. Our findings can be widely applied to guide the design and optimisation of metamaterial mufflers. (C) 2019 Elsevier Ltd. All rights reserved.