Study on the influence of pore structure on the foam concrete towards sound absorption enhancement

The sound absorption performance of porous cementitious materials was constrained by limitations in pore structure optimization, posing significant challenges in achieving high acoustic absorption properties in cement-based materials. In this work, sound absorbing foam concretes with different density, average pore diameter, and open porosity were fabricated through a chemical foaming method followed by a freeze-drying process. Furthermore, the sound absorbing performance, interacting mechanism and compressive strength of the foam concrete were comprehensively investigated. From the result, due to the sound resonance effect and the acoustic impedance matching characteristic, the sound absorbing capacity of foam concrete was closely related to the material's density, and the optimal sound absorbing performance of foam concrete was achieved at an average pore diameter of 3 mm and the open porosity of 73 %. The average sound absorption coefficient and noise reduction coefficient values of the optimal sample have reached 0.49 and 0.43, indicating an increase of 113 % and 169 % compared to foam concrete materials at the same density level. Owing to the good acoustic impedance matching, network-like porous structure, and appropriate open porosity of foam concrete, the transmission pathways of incident sound waves were significantly complicated, the probability of low-frequency sound wave attenuation was increased, and the heat exchange between sound waves and air was also enhanced. Therefore, a remarkable improvement in the sound energy dissipation capacity of foam concrete was achieved, providing a novel strategy for the design of sound absorbing foam concrete. • Sound absorbing foam concretes was fabricated by a foaming and freeze-drying process. • Optimal sound absorbing performance of foam concrete was achieved. • Interacting mechanisms between sound absorption and pore structure was studied. • Novel strategy for the design of sound absorbing foam concrete was proposed.