In building acoustics, the most fundamental aim is to determine the sound power radiated by building elements. In this paper, two methods that are more sophisticated than the conventional measurement of sound pressure in a receiving room are presented and discussed. Both methods, the Discrete Calculation Method and the Integral Transform Method, require only the surface velocity measured in a grid on the radiating surface as input data. Thus the sound power is univocally associated to the considered element. The first assumes a series of radiating piston sources on the surface that move with same velocity and phase relationship as the structure. The second uses spatial Fourier Transformations to determine the radiated sound power in the wavenumber domain, analogous to Nearfield Acoustic Holography. The Integral Transform Method additionally obtains the angle dependent flexural wavenumbers of the structure, which is essential for the analysis of the element dynamics, and as input data for the prediction of sound radiation efficiency and transmission loss of orthotropic building elements, for example, Cross-Laminated-Timber elements. Both methods were applied in some exemplary cases; based on their performance and results, conclusions are drawn on the benefits of both methods.
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