Yasutoshi Kitamura

Sound radiation from a baffled elastic plate strip of infinite length with various concentrated excitation forces

Abstract Recently, problems with elevated structure noise arise around elevated motorways, i.e. noise in the audio-frequency range supposed to be caused by the vibration of the structural elements of an elevated motorway. 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 theoretically analysed in 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 concentrated forces, a line force, a point force, and a concentrated moment, are included in the analysis. The main features of the radiated sound field by the strip are discussed in the light of numerical examples. A parametric study is carried out to clarify the effects of the various parameters of the strip. Furthermore, solutions to the sound radiation from an elastic plate strip of finite length, under the same excitation conditions, are derived and compared with those from the strip of infinite length above. The characteristics of the finite strip are found to be roughly described by those of the infinite strip.

ON RELATIONSHIPS BETWEEN PARTICLE VELOCITY AND VIBRATION LEVEL IN BLASTING VIBRATIONS

This paper consists of two parts; the first is concerned with the proposition of numerical simulation method which computes vibration levels from digital data of vibrations, and the second is for the investigation of relationships between particle velocity and vibration level in blasting vibrations. Although blasting operations have not been included in the subject of the vibration regulation law, the measurement of blasting vibrations as a nuisance to the neighborhood would undoubtedly be performed hereafter by using vibration level meters. Therefore, much attention is paid to discussing the attenuation of vibrations for shock vibrations such as blasting vibrations in this paper. These characteristics of vibration levels are produced by the dynamic characteristics of vibration level meters.