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Study on the Effectiveness of Monte Carlo Filtering when Correcting Negative SEA Loss Factors

Nieradka Paweł, Dobrucki Andrzej

Archives of Acoustics

2023

Vol. 48, No. 2

201--218

The power injection method (PIM) is an experimental method used to identify the statistical energy analysis (SEA) parameters (called loss factors – LFs) of a vibroacoustic system. By definition, LFs are positive real numbers. However, it is not uncommon to obtain negative LFs during experiments, which is considered a measurement error. To date, a recently proposed method, called Monte Carlo filtering (MCF), of correcting negative coupling loss factors (CLFs) has been validated for systems that meet SEA assumptions. In this article, MCF was validated for point connections and in conditions where SEA assumptions are not met (systems with low modal overlap, non-conservative junctions, strong coupling). The effect of removing MCF bias on the results was also examined. During the experiments, it was observed that the bias is inversely proportional to the damping loss factor of the examined subsystems. The obtained results confirm that the PIM, combined with MCF, allows to determine non-negative SEA parameters in all considered cases.

Experimental assessment of coupling loss factors of thin rectangular plates

Panuszka R., Wiciak J., Iwaniec M.

Archives of Acoustics

2005

Vol. 30, No. 4

533-551

Knowledge of Coupling Loss Factors (CLF's) for energy flow evaluation in structural elements of complex mechanical systems is fundamental. Several experiments were conducted to evaluate CLFs of different perpendicular connections of rectangular plates. The method of energy storage was conducted under acoustic free-field conditions, and a large number of thin plates with different designs of junctions were examined. The tests included two types of connections: welded line junction and point junctions. In the first type of connection, the influence of the thickness ratio of plates on CLFs values was tested. In the second type of connection the influence of the point of distribution at junctions on CLFs values were tested. Other tests were done to establish the impact of junction design on CLFs. Welded line junctions have a tendency to decrease the CLFs when the ratio of thickness of plates is increased. The CLFs also increase with density of joining points. Maximal values of CLFs were observed for spot-welded junctions. Mid-values were represented by screw-bolted joints and the lowest values by riveted junctions.