Radiation field prediction system using solutions of exterior steady-stateradiation problem

We have been studying a radiation field prediction system for an acoustic s ource that has an arbitrary shape. First. the nearfield sound pressure dist ribution around the source is measured and the normal velocity distribution over the surface of the source is predicted using the equivalent phased ar ray method (EPAM). Then, radiation characteristics of the source, such as t he pressure field, are predicted using the combined Helmholtz integral equa tion formulation(CHIEF). First in this paper, EPAM based on solutions for t he exterior steady-state acoustic radiation problem is described. This meth od is applicable for predicting the normal surface velocity for sources tha t have an arbitrary shape. Then, an experimental example using a cylindrica l source is presented. The predicted result of the pressure field is shown. and then the validity of this radiation field prediction system is confirm ed by comparing the predicted pressure field with the actual field. The inf luence of the aperture restriction for the measurement contour on the surfa ce of normal velocity predicted by EPAM is discussed. It is found that the error between the predicted and the ideal velocity distribution becomes sma ller as the measurement contour covers the cylinder,