Measurement of structural intensity using a normal mode approach

A method is presented for the measurement of structural intensity using a normal mode approach. This method is tested on an assembly of two plates. The structural intensity field and the divergence of structural intensity are evaluated. The power injected into the structure by a shaker is evaluated in two different ways: directly by measuring the force and the velocity at the excitation point, and by integrating the structural intensity vectors over a closed curve containing the vibration source. There is a close agreement between the results obtained by the two methods.