| Abstrakt: |
The power injection method (PIM) has become widely accepted as a valuable technique to predict the statistical energy analysis (SEA) parameters of a structure in situ. PIM requires the measurement of the power input into every single subsystem and the measurement of the energy level of every subsystem. By inverting the appropriate measured energy matrix, the SEA parameters can be obtained. Conventional PIM suggests to use a more or less predefined number of excitation and response locations. Most often three excitation and five response locations are taken. Due to the spatial variation of the energy density in a subsystem, there will always be a substantial variability associated with the space-averaged energy of vibration and hence associated with the SEA parameters. An accurate SEA model requires accurately measured space averaged energies of vibration and power input levels. The accuracy of the SEA parameters can be assessed by evaluating the confidence levels of the so-called ''normalized energy levels'' and by converting these values into confidence levels of the SEA parameters. This paper aims at presenting the identification procedure of the statistics of the SEA parameters as a function of the number of excitation and response points taken into account during the PIM measurements. In the first place, emphasis will be given to the presentation of the equations dealing with the essential statistical properties of the SEA parameters. It will be shown that by applying straightforward formulas it is possible to assess the accuracy of the estimated SEA parameters and to assess the accuracy of the SEA applications, i.e., vibration prediction, source localization, power flow analysis, sensitivity analysis, etc. Some formulas which are given in this respect will be illustrated by means of SEA results on an irregular box-type structure. © 1996 Acoustical Society of America. [ABSTRACT FROM AUTHOR] |
