Experimental Analysis of the Sound-Absorbing Properties of Reused LDPE Bubble Wrap Packaging for the Sustainable Acoustic Requalification

This study examines the acoustical properties of reused bubble wrap, an LDPE bubble wrap packaging material, as a new sound absorber material. In total, seven different structural designs were experimentally examined through manipulating the number of membrane layers, the thickness of the air cavity, the addition of honeycomb cores, and a unique design of a skein (rolled) configuration to obtain a multilayered structure with interconnectivity of air cavities. The normal incidence Sound Absorption Coefficient (SAC) was measured using an impedance tube as per ISO 10534-2:2023. The experimental data show that the acoustical behavior depends on the structural design and its resonance mechanisms. The best SAC achieved was 0.91 for double-layer and 0.97 for triple-layer membrane structures. Honeycomb cores do not improve the maximum sound absorption coefficient, but they expand the frequency range with high absorption levels above 0.63 in the range of 630 to 1500 Hz. The rolled configuration showed the best broadband performance by having absorptions larger than 0.50 over the 315–1500 Hz frequency range, with a peak value of 0.83 at 440 Hz. A Physics-Informed Conditional Neural Network (PICNN) is used to predict the sound absorption coefficient by incorporating physical constraints on the propagation of acoustic waves. The proposed approach successfully predicted the experimental trend by getting R2 = 0.9905, MAE = 0.0166, RMSE = 0.0242, and NRMSE = 2.49%. The proposed method not convert bubble wrap waste into a useful and eco-friendly acoustic material but also has great potential for designing and optimizing recycled acoustic metamaterials.