Relationships between structural energy density, power flow, and their influence on acoustic intensity.

Abstract

Power flow in structures has been a topic of research for the past few decades. Many different methods for determining structural power flow magnitude and direction have been developed and proven. Structural energy density methods have likewise been developed. In this paper, a study of both structural energy density and power flow in a plate and their influence on the acoustic field is presented. Structural energy density and power flow were determined using equations typically used with accelerometer arrays but adapted for use with a scanning laser doppler vibrometer. Experiments were performed from 25 to 100 Hz by exciting the plate at single frequencies but using different excitation points and methods at each frequency. In some cases two sources of excitation were used to alter the power flow response, giving a broader basis for concluding relationships. Both speaker and shakers were used as sources. The acoustic intensity in the room was calculated at approximately 3 in. from the vibrating plate. Relationships between structural energy density, power flow, and the acoustic field variables are presented.