Investigation on the Low‐Frequency Acoustic Performance of Polymer Matrix Composite With Metallic Hollow Spheres Under Different Acoustic Stack Structures

ABSTRACT In this study, various polymer matrix composites (melamine and flexible polyurethane) combined with 316 L stainless steel hollow spheres were prepared using the casting method. The acoustic properties of the fabricated materials were evaluated under low‐frequency conditions (100–1700 Hz) using an impedance tube. The results indicate that sound absorption and insulation performance are significantly influenced by the incident surface material within this frequency range. Notably, sound waves entering through the polyurethane stainless steel hollow sphere surface yield optimal absorption performance, achieving a maximum sound absorption coefficient of 0.74 at 400 Hz. Conversely, the melamine foam surface provides the best sound absorption at higher frequencies within this range, reaching a coefficient of 0.43 at 1700 Hz. The findings highlight the effective sound absorption and insulation capabilities of the composite materials.