Inoue, A., Tanabe, Y., and Watanabe, M., "An Application of the Particle Velocity Transfer Path Analysis to a Hybrid Electric Vehicle Motor Sound," SAE Int. J. Alt. Power. 2(2):401-411, 2013, doi:10.4271/2013-01-1999.
A pioneering approach to implement transfer path analysis (TPA) is proposed in this paper through applying it to an automobile. We propose to use particle velocity as a measure of TPA, in addition to using sound pressure as a conventional measure for TPA. These two quantities together will give a comprehensive and complete definition of sound. Although sound pressure is a scalar, while particle velocity is a vector, it is also proposed that the same technique of the conventional sound pressure TPA should be independently applicable to each component of particle velocity vector. This has been experimentally verified with a study on our test box system. In this paper, we apply the proposed TPA to an actual vehicle to examine its applicability, advantages and limitations. The driving motor sound of a hybrid electric vehicle is chosen as the case study. A tri-axial particle velocity sensor which also measures sound pressure at the same point is utilized in the experiment. Both structure-borne and air-borne sound paths are considered, and a miniature shaker and a volume velocity source are employed for the frequency response function measurement, respectively. Our results show, for our work on the real vehicle, that our proposed particle velocity TPA works just as well as the conventional sound pressure TPA with comparable error levels. Furthermore, we discuss the details of phase effect in the path rank ordering. While the common approach employs consideration of both amplitude and phase, an alternative treatment may be exercised for sound vector. The analysis presented in this study is limited to the frequency domain. Finally, we briefly touch on the aspect of using sound intensity as a measure of TPA.