Development of a dry-type double floor with high vibration isolation for improvement of floor impact sound insulation performance on CLT buildings

To improve the floor impact sound insulation performance of cross laminated timber (CLT) buildings, a box-type test chamber made of CLT was constructed, and the countermeasure using a dry-type double floor was investigated. Several specimens with different area density and bending stiffness of double flooring structure were prepared, and the materials of flooring and elastic floor posts were adjusted so that the natural frequency of each specimen was about 14 Hz when the specimen was considered as a single-degree-of-freedom system. The dry-type double flooring structure affected the response at the natural frequencies not only of the slab but of walls. When installing the dry-type double flooring structure, the influence of acoustic radiation from the ceiling surface was relatively high at lower frequencies, while at higher frequencies, the influence from the walls was relatively high. The installation of the dry-type double flooring structure resulted in an improvement in floor impact sound insulation performance.