# Development and Characterization of a Flexible Soundproofing Metapanel for Noise Reduction
###### Abstract  
This study addresses the critical challenge of developing lightweight, flexible soundproofing materials for contemporary applications by introducing an innovative Flexible Soundproofing Metapanel (FSM). The FSM represents a significant advancement in acoustic metamaterial design, engineered to attenuate noise within the 2000-5000 Hz range--a frequency band associated with significant human auditory discomfort. The FSM's novel structure, comprising a box-shaped frame and vibrating membrane, was optimized through rigorous finite element analysis and subsequently validated via comprehensive open field tests for enclosure-type soundproofing. Our results demonstrate that the FSM, featuring an optimized configuration of urethane rubber ([PERSON]'s modulus 6.5 MPa) and precisely tuned unit cell dimensions, significantly outperforms conventional mass-law-based materials in sound insulation efficacy across target frequencies. The FSM exhibited superior soundproofing performance across a broad spectrum of frequency bands, with particularly remarkable results in the crucial 2000-5000 Hz range. Its inherent flexibility enables applications to diverse surface geometries, substantially enhancing its practical utility. This research contributes substantially to the rapidly evolving field of acoustic metamaterials, offering a promising solution for noise control in applications where weight and spatial constraints are critical factors. acoustic metamaterials; flexible soundproofing metapanel; noise reduction; sound transmission loss +
Footnote †: journal: Applied  
doi: 10.3390/0004-4691/2000-0000-0000-0000-0000-0000-0000-0000-0000-00000-000  
lightweight soundproofing structures [19; 20; 21; 22]. These metamaterials utilize thin, lightweight structures to dissipate noise energy effectively. For instance, a membrane acoustic metamaterial (MAM) combined with a minuscule rigid mass exhibits extraordinary noise reduction capabilities at low frequencies owing to its negative dynamic effective density [23; 24; 25]. Recent advancements have led to the development of lattice-based soundproofing AMMs, which offer distinct advantages in durability and ease of manufacture [16; 17; 26]. These structures achieve high sound transmission loss (STL) by realizing negative effective material properties. The periodic arrangement of these lattice structures creates destructive interference patterns for sound waves, effectively trapping them within the unit cells. Additionally, by maximizing the mismatch in acoustic impedance between the structure and the surrounding medium, these AMMs can significantly enhance sound wave reflection [23; 27]. However, the inherent rigidity of most of these structures limits their application to various surface geometries, and they often exhibit a rapid decrease in STL near resonance frequencies. Consequently, a pressing need exists for a novel AMM class that maintains flexibility while providing effective noise reduction capabilities across a broad frequency spectrum. Our study addresses the technological gap in lightweight soundproofing by introducing a Flexible Soundproofing Metapanel (FSM), engineered to attenuate noise within the 2000-5000 Hz range, a frequency band that induces significant auditory discomfort in humans [28]. This innovative design maintains structural flexibility while targeting a crucial spectrum of noise pollution, facilitating its application to diverse curved or irregular surfaces. The FSM demonstrates superior performance efficiency compared to mass-law-based control groups, achieved through an innovative flexible membrane-type acoustic metamaterial design. It results in a lightweight, thin structure that effectively mitigates noise in the target frequency range. A key innovation of the FSM lies in its capacity to generate multiple eigenmodes through the relative motion of the membrane and frame. The superposition of these out-of-phase eigenmodes produces anti-resonances, wherein the vibration displacement of the thin soundproofing frame is substantially reduced.