A laser technique which measures vibrational energy flow (intensity) via propagating bending waves is described. A pair of scanning laser beams from a two-channel laser vibrometer is used to provide a nonintrusive measurement of the intensity at various points on a vibrating beam. Results are shown to compare well with those of two additional techniques. These techniques, used for validation, employ a single laser beam and can only be used at resonance frequencies in beams or rods. The two-channel laser technique described can be applied to two-dimensional intensity measurements, is not limited to single frequency excitation, and has an inherent capability to facilitate phase error elimination via a photodetector switching technique which is also described.

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