Abstract
This paper is concerned with a new procedure to determine an optimal shape of sound-insulating wall for auto-highways. A two dimensional cross-section of the wall is optimized by using the boundary element method (BEM) together with cellular automata (CA). In application of CA, a feasible area of the wall is divided into a number of uniform cells, and all the state variables defined on each cell are changed by a transition rule, e.g. minimizing a cost function, under a local rule for neighbor cells so that a final state of cells can be determined. In this paper, a new transition rule is proposed to find the final state of cells which may reduce noise. The reduction of noise is monitored by the mean absolute value of sound pressures measured at several points. It is assumed that a point noise source is placed at the center point of the road. Numerical computation is carried out for a typical model of the sound-insulating wall. Through discussion on the results obtained, it is revealed that the proposed procedure for estimationg an optimal shape of the sound-insulating wall is rather robast for a wider range of sound frequencies.
