A technique for the assessment of strength of coupling between statistical energy analysis subsystems

One of the main requirements for the successful use of traditional Statistical Energy Analysis (SEA) is to select weakly coupled subsystems. In particular, the method of energy matrix inversion to determine loss factors by experiment can be subject to serious error if subsystems are strongly coupled.The objective of this research is to develop a simple and rapid experimental test of coupling strength in a SEA sense. On the basis of Langley's definition of weak coupling, a convenient way to assess the strength of coupling is described through theoretical and experimental studies of one-, two- and three-dimensional coupled subsystems. It appears that, in case of resonant coupling, when one subsystem is subject to impulsive excitation, the time delay in the rise of the kinetic energy in the indirectly excited subsystem can be used to define an effective indicator of strength of coupling. This indicator, CS, can be used on assembled structures prior to a SEA analysis and gives an absolute scale of strength of coupling for the systems studied. However, the requirement of resonant coupling for CS to be valid could be a major shortcoming if any attempt is made to apply SEA to systems with low modal density. Therefore, on the basis of a theoretical model of energy impulse response, a statistical indicator of resonant coupling named Mp is proposed. Although further investigations are necessary to validate Mp, both indicator CS and MP used together should provide a reliable assessment of strength of coupling in a SEA sense.