Modal Sampling Technique on Reception Plate to Characterize Structure-Borne Sound Source

In heavyweight buildings, standardized methods exist to predict sound levels in neighboring rooms produced by airborne and structure-borne sound sources. Input data for these predictions are the airborne and structure-borne sound power of the source. The airborne sound power is commonly characterized by measuring the sound pressure at various positions in a diffuse airborne field (reverberation chamber), whereby structure-borne sound power is characterized by measuring the spatial-average velocity in a structurally diffuse filed (reception plate). In both mediums problems can arise at low frequencies, at which a non-diffuse field could be present due to the low number modes. There are different ways to tackle this problem. This paper focuses on an approach to characterize the structure-borne sound power through numerical investigations on a validated finite element reception plate model. Here, a sampling technique is presented, in which the structure-borne sound power of the single low frequency modes is determined using spatial Fourier transformation. The total power injected into the reception plate from the source is calculated through summation of the modal powers. These results are compared to the results obtained from other approaches and through FEM simulations of the direct injected power at the driving-point.