Efficient numerical prediction and experimental validation of impact sound radiation by timber joist floors

Timber joist floors are widely applied in residential buildings. The accurate impact sound radiation prediction of a bare timber joist floor is characterized by three main challenges. First, the prediction of the impact force on a timber joist floor is more difficult than that for a traditional heavyweight floor, since the low impedance of the timber joist floor induces more complex interaction between the excitation source and the floor. Second, the dynamic behavior of the floor is strongly affected by several characteristics, such as the finite dimensions, plate-joist coupling, orthotropic mechanical properties, boundary conditions, etc. Third, it is difficult to efficiently compute the precise acoustic field for the whole building acoustic frequency range. This work proposes a two-step numerical prediction model for impact sound radiation. First, the impact force of the ISO tapping machine is computed, considering the floor-hammer interaction. Second, the vibration field is accurately computed by a detailed finite element model of the floor, and the sound field in the room is subsequently computed by an efficient diffuse field model. This prediction model is experimentally validated in a case study of a timber joist floor. Differences between the measured and computed normalized impact sound pressure level according to ISO 717-2 did not exceed 2dB.