Numerical Investigation of the Sound Insulation Performance of Sandwich RC Slabs with Interlayer Inclined Rebar Connectors

To balance load-bearing capacity and acoustic insulation, this study proposes a sandwich reinforced concrete (RC) slab with W-shaped interlayer inclined rebar connectors and investigates their influence on acoustic bridging. A three-dimensional vibro-acoustic finite element modeling approach was adapted to analyze airborne sound insulation and impact sound pressure levels in the frequency domain and was validated against experimental results. Parametric analyses were then conducted to evaluate the effects of connector number, connector geometry, anchorage-end treatment, and core-layer parameters. The results revealed distinct frequency-dependent behavior. The introduction of connectors produced a stable dip in airborne sound insulation near 400 Hz and a pronounced impact-sound peak within 200–400 Hz, both associated with connector-controlled coupled characteristic frequencies. Increasing the number of connectors strengthened interlayer stiffness coupling and intensified acoustic bridging in these frequency ranges. By contrast, optimizing the connector structure or introducing a compliant end layer reduced coupling and improved acoustic insulation. Overall, acoustic performance can be improved by reducing the equivalent coupling stiffness of the connectors, enhancing energy dissipation at the connector ends, and appropriately selecting the core-layer parameters. These measures help suppress the characteristic-frequency response and improve mid- to high-frequency sound insulation.