Measurement of the Structural Intensity

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The purpose of this study were to test the accuracy of structural intensity measured by the so-called two accelerometer method and to discuss the application of the method to the problems of noise and vibration of structure.Following results were obtained in this study:(1) The accuracy of vibrational power measured by an impedance head was tested by a mechanical method and an electrical one. It was observed that the vibrational power was accurately measured.(2) The accuracy of a structural intensity measuring system was tested using a steel beam partly covered by damping material. Specifically, the vibrational power supplied by the exciter was measured by an impedance head. The vibrational power was calculated based on the structural intensity measured on the beam. The accuracy of the measuring system was found to be sufficient by comparing the calculated power with the measured one.(3) The accuracy of the structural intensity measuring system was tested using a flat steel plate partly covered by damping material. Specifically, the vibrational power supplied by the exciter was measured by an impedance head. The vibrational power passing closed lines encircling the exciting point and straight lines intersecting the plate laterally was calculated based on the structural intensity measured on the lines. The accuracy of the measuring system was found to be sufficient by comparing the calculated power with the measured one.(4) An FEM based computer program was developed to calculate the structural intensity on the flat plate with damping material. The sufficient accuracy of both the measurement and calculation of structural intensity over the plate was observed by comparing the calculated distribution with the measured one. In addition the influence of damping materials on the mode of vibrational power flow was examined.(5) The relation between the structural intensity distribution and the movement of nodal lines of bending vibration of the plate was discussed.