A mechanically adjustable acoustic metamaterial for low- frequency sound absorption with load-bearing and fire resistance

Broadband sound absorption is limited to discrete noise with abrupt peaks in the spectrum. Here, we proposed a mechanically adjustable acoustical metamaterials (AAMM) for low-frequency sound absorption with deep-subwavelength (0.025 lambda), which integrates Helmholtz resonators and Fabry-Perot (FP) tubes by precise modular design. The calculation results based on the theoretical model demonstrate that the broad low frequency (from 100 Hz to 500 Hz) tunability of the composite adjustable sound absorbing materials. The adjustable design scheme is further verified by numerical simulation. Then a multi-impedance adjustment method is proposed to improve the local optimal defect and make it have quasi-perfect sound absorption effect in the range of 120 Hz-348 Hz. The sound absorbing material sample can withstand 2.7 tons of dynamic load and 1300 degrees high temperature, presenting superior compression and fire resistance compared to conventional porous sound absorbing materials and membrane acoustic metamaterials. This research on assembled machine-adjustable sound absorption material enriches the conventional acoustic metamaterial design scheme, further improves the space utilization rate, and provides an effective solution for dealing with low-frequency complex variable noise.

Automated summary

This study presents a mechanically adjustable acoustical metamaterial (AAMM) for low-frequency sound absorption. By integrating Helmholtz resonators and Fabry-Perot (FP) tubes, a deep-subwavelength material with broad low frequency tunability is achieved. The multi-impedance adjustment method is used to improve the sound absorption effect and provide better compression and fire resistance compared to traditional materials.