Design of a broadband composite noise reduction metamaterial with integrated vibration reduction and sound absorption and insulation

In traditional noise and vibration control problems, researchers typically concentrate on a single type of sound insulation, sound absorption, or vibration reduction. It is not enough for noise control in complex environments. To address this challenge, this paper proposes a broadband noise and vibration reduction metamaterial (BNVRM) that integrates sound insulation, sound absorption, and vibration reduction into one multi-functional system. The composite structures consist of a spindle-shaped phononic crystal plate, Fabry-Perot sound absorption channels, and a micro-perforated plate. Firstly, based on the finite element method, the vibro-acoustic model of the BNVRM is established. Subsequently, each structure is studied separately as a single variable to investigate in-depth the vibro-acoustic mechanisms and parametric influence laws of different materials or structures. Finally, a material and structure optimisation design of the BNVRM is conducted based on specific frequency and noise reduction requirements. The results demonstrate that compared to a same mass homogeneous plate, the total noise reduction effect of the BNVRM is improved by 3.5 dB(A). After optimising the structural parameters, the noise reduction performance can be further improved to 7.4 dB(A). These findings provide a scientific reference and basis for the design of multi-functional noise and vibration reduction materials or structures in complex vibro-acoustic environments.