An experimental comparison of the sea power injection method and the power coefficient method

A new method, the power coefficient measurement method, was proposed recently by Fahy to measure power transfer and dissipation coefficients. In this paper, the feasibility of this new method is experimentally tested based on a two-plate system. The power injection method is used as a reference to assess the accuracy of the new method. Measurements were carried out under two types of source: continuous steady (shaker) excitation and repeated impact (hammer) excitation. The estimation was made based on two formats of data: velocity autospectra and velocity transfer functions. It is shown that the new method can give comparable results to the power injection method at frequencies where the modal overlap factor is larger than 1. Either the data-recording format or the source type has little impact on the measurement accuracy. The data can be recorded in the format of either velocity autospectrum or transfer function. At frequencies where the modal overlap factor is less than 1, the approximation error of the new method is large resulting in an overestimation.