Sound Insulation of Houses Built on Prefabricated Slabs
The sound insulation performance of houses built on prefabricated slabs is generally poor, mainly affected by factors such as slab characteristics, sound transmission principles, and construction techniques.
Regarding slab characteristics: The prefabricated slabs from the 1980s and 1990s were relatively thin and had numerous joints, which significantly impaired sound insulation. However, these slabs were mostly made of solid concrete, with a large overall mass, providing good resistance to airborne sound transmission. Sounds like speech and television noise were less likely to travel downstairs. Nevertheless, impact sounds such as footsteps were clearly transmitted, with a very 'solid' impact feel. This is because impact sounds are transmitted through solids, differing from the principle of airborne sound transmission. While a large slab mass can block airborne sound, it struggles to block solid-borne sound.
Regarding sound transmission principles: When sound travels from upstairs to downstairs, impact sounds are the primary concern. Objects directly hitting the slab generate vibrations that propagate downward through the solid structure, almost impossible to block with ordinary decoration materials. Moreover, impact sounds also spread horizontally along walls, columns, and pipes, resulting in a wider sound diffusion range. Additionally, humans are particularly sensitive to low-frequency impact sounds; even if the sound is not loud, it can still cause discomfort.
Regarding construction techniques: Prefabricated slabs are manufactured in factories and then transported to the site for hoisting. The connection between slabs is achieved by filling mortar and creating node connections. This connection method generally results in lower overall stiffness compared to fully cast-in-place structures. In the event of earthquakes or uneven foundation settlement, slab joints, connections, and load-bearing walls are more prone to problems, thereby affecting sound insulation. Furthermore, some prefabricated slab residential areas built in the 1980s and 1990s lack complete ring beams and structural columns in buildings, and the slab end ties and support lengths are not as strict as current standards, leading to issues such as ceiling water leakage and fine wall cracks. These problems also indirectly result in poorer sound insulation between floors.
Comparison with new houses: Current commercial housing, in pursuit of floor height and cost control, generally has thinner slabs. In some projects, the ground is constructed by laying insulation or sound insulation materials on the structural slab, followed by pouring a very thin leveling layer, and then laying flooring or tiles. If the materials and construction are compromised, the sound insulation effect will be poor. However, in recent years, some regions have begun to mandate sound insulation measures for residential slabs, such as floating slabs with sound insulation pads as the surface layer. However, the degree of enforcement varies across regions and time periods, resulting in differences in sound insulation performance.
