SOUND RADIATION FROM A BAFFLED ELASTIC PLATE STRIP OF INFINITE LENGTHWITH VARIOUS CONCENTRATED EXCITATION FORCES

Recently, problems with elevated structure noise arise around elevated motorways, i.e, noise in the audio-frequency range supposed to be cau sed by the vibration of the structural elements of an elevated motorwa y. The measurement data shows that steel plate girders may be the main source of the elevated structure noise. Therefore, the radiated sound field generated by a baffled elastic plate strip of infinite length, which is the simplest model of the web of a steel plate girder, is the oretically analysed ill this paper. A far-field approximation solution is derived in a closed form. Since the actual condition of the strip excitation has never been clarified so far, three kinds of possible co ncentrated forces, a line force, a point force, and a concentrated mom ent, are included in the analysis. The main features of the radiated s ound field by the strip are discussed in the light of numerical exampl es. A parametric study is carried out to clarify the effects of the va rious parameters of the strip. Furthermore, solutions to the sound rad iation from art elastic plate strip of finite length, under the same e xcitation conditions, are derived and compared with those from the str ip of infinite length above. The characteristics of the finite strip a re found to be roughly described by those of the infinite strip. (C) 1 998 Elsevier Science Ltd. All rights reserved.