Vibration and Sound Radiation of Visco-Elastically Damped Plates. Acoustic Power Radiation of Point-Excited Beams.

Abstract

The effects of structural damping and wavenuwmber ratio on the acoustic power radiated by point-excited damped infinite beams and simply supported finite beams with same cross sections have been studied. The numerical calculations of the acoustic power were carried out using Keltie's equations based on the Heckl's power integral. The acoustic medium is assumed to be air, and the effect of the back reaction of the sound field is neglected in the beam response equation. Non-dimensional acoustic power, sound radiation efficiency, and acoustic power conversion efficiencies are presented as functions of wavenumber ratio and beam loss factors. It is shown that the power conversion efficiency of the infinite beam is inversely proportional to the wavenumber ratio and independent of the loss factor below coincidence, and is approximately proportional in inverse to the loss factor above coincidence. The power conversion efficiency of the finite beam has dull peaks with values roughly inverse-proportional to the loss factor at nonresonant frequencies. The similarity of acoustic power radiation between infinite beams and finite beams has been observed when the length and loss factor of beams is increased.