Collaborative Research: Can Irregular Structural Patterns Beat Perfect Lattices? Biomimicry for Optimal Acoustic Absorption

This grant supports the advancement of novel architected material systems that exploit irregular geometric patterns to produce unparalleled control over acoustic wave absorption, impedance, and frequency bandwidth. Taking inspiration from the Fibonacci pattern found in sunflowers, this research will establish new design principles for irregular geometric patterns, thus revolutionizing current geometric designs in lattices. Irregular designs of acoustic architected materials offer two groundbreaking achievements, currently unattainable through regular designs: enhanced control of nonlinear wave dynamics and expanded attenuation bandwidth. This research will deepen the current understanding of the physics underlying the relationships between geometric variations and collective wave dynamics in artificially engineered and architected materials,and will catalyze the development of the next generation of patterned materials for diverse engineering applications involving acoustic, electromagnetic, and photonic sources or detectors. Reparative learning development activities will target schools in socioeconomically disadvantaged, noise-impacted communities to demonstrate the efficacy of affordable irregular pattern metamaterials in mitigating the recent surge in noise from aircraft jets and airports that adversely affects these communities. Beyond classroom activities, the project aims, through collaboration with community activists, at empowering and enabling these communities to create their own adaptable and economically viable alternatives to current, often toxic, acoustic absorption products. This NSF project will develop models and experimental prototypes that establish the physical laws behind, and practical applications of, geometric variants in engineering irregular patterned material systems. The models are based on a continuum approximation to forecast the impact of commonly occurring geometric variations found in nature on the dynamics of acoustic waves in resonant lattices. Irregular patterns will be characterized by geometric variants of the resonators’ rigidity and proximity. Utilizing this model, we will optimize absorption, impedance, and phase properties while expanding the frequency range within irregular lattices, with these properties being functions of the mentioned geometric variants. Building on the insights gained from the models, acoustic attenuation will be executed through prototype designs. Each panel will incorporate Helmholtz resonators featuring both regular and irregular Fibonacci patterns. The primary objective is to mitigate sound in the 200-2000 Hz frequency range, known to be detrimental to human hearing and health, such as noise from highway traffic, aircraft jets, trains, airports, and construction activities. The demonstration prototypes will take the form of indoor and outdoor acoustic attenuation panels designed for integration into buildings. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.