Energy distribution of structureborne sound in built-up structures

  • Hugin, Claus Thomas (Project Manager)
  • Ohlrich, Mogens (Project Participant)

    Project Details

    Description

    Noise from machinery and in vehicles is often caused by the structural vibrations of components and panels. Reducing such noise therefore requires that one can predict the energy distribution and vibration levels of quite complex structures. The so-called Statistical Energy Analysis (SEA) has proved to be a useful and reliable method if the structure has a high modal density. This is usually the case at high frequencies, but the assumption may be violated in the acoustically important mid-frequency range where the modal density of practical structures is often only moderate or even low. In this project it has been demonstrated that the inherent requirement of SEA can be relaxed if the re-transmission of power between coupled, finite subsystems is taken into account by a mean value calculation. This makes it possible to predict the energy distribution of the subsystems, and results in a coupling loss factor that can be used in an SEA prediction also at a moderate modal density.
    The method is based on a 'ray tracing' approach that involves the Helmholtz number of each element and the reflection and transmission coefficients of the connections. This approach has been examined for power transmission by flexural waves in coupled beam structures, and the results have been published in the Journal of Sound and Vibration in 1998.
    StatusFinished
    Effective start/end date01/08/199501/02/1998

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