In-plane Laser-Doppler-Velocimeter sensor head for the measurement of surface structural intensity

The existing theory regarding the acoustic Poynting vector in the free surf ace of a structure, which up to now has only been established for the case of isotropic structures, is generalized to non-isotropic structures. It is shown that, in this general case, the measurement of the acoustic Poynting vector in the surface can be reduced to a measurement of the three in-plane strain and the two in-plane velocity components. Based on this formulation , a sensor head concept for the determination of the acoustic Poynting vect or, using multi-point optical in-plane displacement measurement is presente d. The concept is studied experimentally for a simple case of one-dimension al structural vibration. Experimental results obtained with a sensor head d esigned for one-dimensional acoustic energy flow are presented, demonstrati ng the feasibility of the technique.