Abstract:

The application of the BEM (direct form) for the external domain, with a lineal combination of Helmholtz's equation integral and their derivative (Burton, Miller) makes possible the calculation of the unique solution for each number of waves. The fundamental characteristics of this model that works with lineal sound source are: (1) The calculation surface is the topographical profile adapted with adjacent plans, discertizated in elements defined by two extreme nodes and one central node. (2) The acoustic impedance of each element is determined starting from the Delany equation. (3) The unknowns are the sound field in each node (phi)[inf i]. (4) A form function (phi) is determined starting from the (phi)[inf i] of each node. (5) Helmholtz's operators are obtained by integrating the (phi) function in each element. (6) By solving the equation system with these operators, the values of the (phi)[inf i], and the function (phi), are obtained. (7) By integrating Helmholtz's equation integral starting from (phi), the value of the sound field in each point of the space is gotten. Finally, the model is applied to several simple barriers for which there are experimental values. The comparison of the obtained outputs shows the validity of the calculation.