Low-frequency soundproof concrete

A low-frequency soundproofing concrete has been developed. In this type of concrete, lead spheres coated with silicone rubber are used as aggregates, the lead ball being heavy and rigid, and the silicone rubber light and soft. The coated lead spheres are uniformly embedded into a short fibre reinforced cement-based matrix. When a sound wave approaches such a concrete panel, localised excitation in the coated lead balls will be induced at certain frequencies. Resonant excitation can consume a considerable amount of energy and thus the sound transmission through the panel at these frequencies can be greatly reduced. Experimental results show that concrete with the embedded coated lead spheres produces resonance at about 150 Hz and also improves the sound insulation at the low frequency range.