Activated carbon-reinforced polyurethane composite foams with hierarchical porosity for broadband sound absorption

The generation of various noise has caused severe noise pollution issues across a wide frequency spectrum, urgently requiring the development of sound-absorbing materials. Herein, we introduce composite polyurethane (PU) foams incorporating extremely nanoporous activated carbon (AC) including both meso- and macro-sized pores as an eco-friendly sound-absorbing material with superior and broadband sound absorption capabilities. The composite foam absorbs 95.8 % of the incident acoustic waves in the 2,000–5,000 Hz frequency range, i.e., the most sensitive range for the human auditory system, far outperforming pristine PU foam, which absorbs only 70.6 %. We demonstrate that sound absorption properties can be fine-tuned by adjusting the pore type and content of the AC. Significantly, the optimized composite foam structure absorbs 100 % of the incident waves at a specific frequency of 2,550 Hz. Collectively, we propose a master curve for the sound absorption properties derived from various composite foams, demonstrating that the properties can be precisely predictable and subsequently used for designing the pore characteristics and content of AC. Incorporating AC can also improve the mechanical properties of foams through interfacial adhesion phenomena. Our methodology provides valuable insights into the fabrication of composite foams with tunable sound absorption properties as a promising solution to noise pollution.