Broadband low-frequency sound absorption and high insulation in a clay-cement composite with hydrogel-foaming engineered gradient porosity

Urban noise pollution has emerged as a critical environmental issue, driving demand for high-performance cementitious materials with broadband sound absorption capabilities. Conventional porous concrete, characterized by uniform pore distribution, suffers from narrow absorption bandwidth and low sound insulation, limiting its practical application in architectural acoustics. To address these limitations, this study developed Clay-based mixed cement mixed with water gel particles and foaming agent sound-absorbing material (CCWGP&FA) by incorporating hydrogel particles and foaming agents to optimize pore structure. Systematic evaluation using impedance tube measurements and complementary characterization techniques revealed outstanding acoustic performance: an average sound absorption coefficient of 0.64 across 300–1500 Hz, peaking at 0.75 within 421–437 Hz. The material demonstrated superior sound insulation with mean transmission loss reaching 37.94 dB across tested frequencies, featuring prominent peaks of 55.66 dB at 784 Hz and 53.24 dB at 553 Hz. The multiscale gradient pore architecture enhances acoustic energy dissipation through synergistic viscous friction, thermal damping, and hierarchical resonance mechanisms particularly improving mid-to-low frequency absorption. This innovative absorber holds significant theoretical and practical value for architectural applications, offering a novel strategy for developing broadband sound-absorbing construction materials.