Numerical and experimental investigation of the effect of geometric parameters on the acoustic performance of bio-inspired reed structures

In recent years, rapid economic development and urbanization have led to serious environmental problems, including noise pollution. Although existing acoustic absorbers can be designed to target specific frequency ranges, those effective at low frequencies typically require large volumes. Consequently, there is a growing demand for compact absorbers capable of mitigating low-frequency noise in the range of 100-1500 Hz. Conventional liners, such as melamine foam, exhibit limited performance in this frequency band. To address these limitations, NASA patented a broadband acoustic absorber inspired by natural reeds, which mimics their geometry and sound absorption characteristics. This study investigates the influence of reed diameter, orientation angle, and spacing on the sound absorption performance of reed-inspired structures. Models with reed spacings of 6 mm, 8 mm, and 10 mm and reed angles of 45° were developed for reed diameters of 3.5 mm and 5 mm using SolidWorks. Numerical simulations were performed in COMSOL Multiphysics based on the Delany-Bazley model. The results indicate that a configuration with a 5 mm reed diameter, 8 mm spacing, and a 45° orientation achieves the highest sound absorption coefficient. Sound pressure measurements further confirmed the effectiveness of the optimized design, showing a reduction from 92.3 dB to 48.1 dB in the numerical analysis and from 91.4 dB to 57.1 dB in the experimental measurements, corresponding to an average sound pressure reduction of approximately 47.8%. Despite minor discrepancies between numerical and experimental results, the findings demonstrate that bio-inspired reed-like structures provide efficient and compact low-frequency noise attenuation. Overall, this study shows that careful geometric optimization of reed-inspired absorbers can bridge the gap between idealized numerical predictions and experimental performance, offering a promising approach for developing compact, high-efficiency solutions for low-frequency acoustic control in aerospace, automotive, industrial, and architectural applications.