Improvement of sound absorption characteristics of honeycomb sandwich panel with heterogeneous micro perforations using numerical analysis

This study presents a systematic optimization approach for enhancing the broadband sound absorption performance of micro-perforated honeycomb sandwich panels through controlled grading of perforation diameters and strategic perforation distribution. While previous research has explored heterogeneous micro-perforations with randomly distributed diameter ratios, the critical role of occupancy rates for each perforation diameter in achieving optimal absorption bandwidth has been overlooked. A coupled COMSOL Multiphysics-MATLAB optimization framework was developed using LiveLinkTM to sequentially determine optimal occupancy rates for each perforation diameter. The optimization algorithm targeted perfect absorption at specific resonance frequencies, automatically adjusting occupancy rates for each perforation diameter. Finite element analysis (FEA) employing thermoviscous acoustics was performed to evaluate absorption characteristics across 500-2200 Hz. Results demonstrate that optimized occupancy rates (i.e. 18, 13.5, 8, 5.5 and 3 percentage for perforation radii 0.5-1.1 mm) achieves a bandwidth of 1100 Hz at 0.8 absorption coefficient (990-2050 Hz range), representing a 120 percentage improvement over randomly distributed configurations reported in literature (at absorption coefficient 0.8 with 500 Hz bandwidth). The optimized design exhibits critical coupling of resonant peaks through constructive interference, producing smooth broadband absorption rather than isolated peaks. A larger panel configuration (14 cm x 14 cm) demonstrated 190 Hz bandwidth at 0.8 absorption in the lower frequency range (310-500 Hz). This work establishes that systematic optimization of occupancy rates is essential for maximizing absorption bandwidth in heterogeneous micro-perforated acoustic absorbers.