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This paper presents the results of an experimental test campaign carried out on a city bus powered by serial hybrid power train. The driveline system combines an Internal Combustion Engine with a battery pack and two electric motors. Tests were aimed at identifying the salient signal characteristics of the noise spectra recorded during operating conditions and to assess the acoustic comfort in the passenger compartment. Transfer Path Analysis technique was applied to identify airborne and structure borne vibro-acoustic loads, to measure transfer functions linking source locations to target locations and to estimate the internal vibro-acoustic comfort in operating conditions.

The paper will introduce some recent advances in vibration testing and modal analysis of airplanes. Recently, a very promising parameter estimation method became available, that has the potential to become the new standard. The main advantage of this so-called PolyMAX method is that it yields extremely clear stabilization diagrams even for broadband and high-order analyses. The method will be applied to two aircraft cases: a Ground Vibration Test using broadband shaker excitation on a small composite aircraft and in-flight data using natural turbulences as excitation. These two data sets allow illustrating both the classical Frequency Response Function based as well as the operational output-only modal analysis process.