A Hybrid Model For Vibroacoustic Studies

The acoustic field generated in a hard-walled, fluid-filled cavity by the random vibration of one thin flexible wall is analysed in terms of a hybrid deterministic-probabilistic model. This approach implies that the flexible wall is not amenable to a deterministic treatment owing to its high modal density and uncertainties concerning its exact geometric and material properties. Thus, a probabilistic treatment, based on vibration field correlation characteristics, is proposed for the wall. On the other hand, complete information is available for the cavity, making it tractable by deterministic acoustic modal analysis. A coupling coefficient between each acoustic mode and the wall bending wave field is employed to represent the vibroacoustic interaction, and the response obtained from a modal summation of the contributions from each acoustic mode. Comparisons are presented with experimental results obtained on a system which consists of a rigid rectangular box with one flexible wall. It is shown that narrow band and frequency-averaged sound pressure levels approach the experimental results provided that more than eight plate modes are available in the frequency band of analysis, or that the plate modal overlap factor is greater than unity.