Implementation of a Numerical Method for the Best Fitting of the Bending Stiffness Curve to a Set of Experimental Points

Industries working in the automotive and building fields are very interested in the determination and the prediction of the sound reduction index given by lightweight partitions. The investments in this research field are aiming in finding experimental methods capable to assess the sound insulation performances of small specimens. Using some expensive software based on FEM-BEM methods they aren't taken into account some variables influencing the sound transmission index and deriving from the manufacturing stage.Some methods based on the determination of the dynamic properties of sandwich beams have been developed and validated. The actual bending stiffness of the beam specimen has to be determined on the basis of the least mean square method applied on a set of frequency dependent bending stiffness points determined for each natural frequency of the beam tested in free-free conditions. It has been proved that the application of the least mean square method is not straightforward and requires a progressive approach in order to correctly fit the curve to the experimental points in the high, medium and low frequency ranges.In this paper an alternative numerical method able to find a better fit of the theoretical bending stiffness curve to the experimental points is proposed.