Experimental study on floor impact sound reduction by double ceiling system with cross laminated timber panels

Aiming to improve the floor impact sound insulation of cross laminated timber (=CLT) floor slabs, authors proposed double ceiling systems with CLT panels of its thickness 90mm. CLT floor slab and several variations of CLT ceiling specimens were installed in the laboratory, and their floor impact sound levels were measured. Results of those experiments are as follows. (1) In case of a CLT double ceiling with 120mm air cavity and closed, approximately 10dB improvement was observed only in light floor impact sound insulation performance. (2) In case of its air back cavity opened to the sound receiving room, both heavy/soft and light floor impact sound levels in the sound receiving room became higher. (3) In case of a CLT double ceiling system with 158mm air back cavity opened to horizontal direction, air pressure increasing in the back cavity and vibration of ceiling panels were suppressed. In this case, heavy/soft floor impact sound insulation performance was improved. (4) Further, by loading weights of sand bags on CLT ceiling panels with 196mm air cavity and opened to the horizontal direction, heavy/soft floor impact sound level index (= L number) decreased by eight points from the case without a ceiling system.