The prediction of sound field in cavities surrounded by vibrating walls is a simple task nowadays, provided that the velocity distribution along the walls is known in sufficient detail. This information can be obtained from a structural finite element (FE) calculation of the building and the results can be fed directly into a conventional boundary element (BE) analysis. Though methodically simple, it is not an attractive way of prediction from the practical point of view: the size of the matrices needed for BE calculation is too large, thus their inversion is very cumbersome and computationally intensive.
The paper introduces a modified numerical calculation method appropriate for practical calculations without the need to construct and invert large matrices. The suggested method is based on the Rayleigh radiation integral and some standard direct (collocational) BE techniques, where the necessary input data are generated from measured or calculated velocity values at just a few points. The technique has been compared and validated on the basis of an extensive measurement series, performed in a reinforced concrete frame building close to a tunnel of line RER B of the underground railway network in Paris.