A NOTE ON THE VIBRO-ACOUSTIC RESPONSE OF A PERIODICALLY SUPPORTED BEAM SUBJECTED TO A TRAVELLING, TIME-HARMONIC LOADING

The effects of periodic spring supports on the acoustic response of an infinite, fluid-loaded beam subjected to a travelling, time-harmonic loading are investigated. To account for the numerous wavenumber components caused by the elastic supports; the wavenumber- harmonic series proposed in previous study (C. C. Cheng et al. 2000 Journal of Vibration and Acoustics ASME) is used to represent the transverse response. Results show that for a periodically, elastically supported beam subjected to a nearly stationary force, an acoustic radiation peak occurs when the excitation frequency coincides with one of the bounding frequencies of the propagation zones. Furthermore, each enhanced acoustic radiation will split into two peaks due to the Doppler shift when the harmonic force becomes travelling and a formula based upon equations of propagation constant and the Doppler effect is derived to help determine the wavenumber ratios corresponding to these peaks.