Far field extrapolation technique using CHIEF enclosing sphere deduced pressures and velocities

by Robert M. Drake

A Combined Helmholtz Integral Equation Formulation (CHIEF)-defined enclosing sphere placed around an acoustic projector is used to calculate far field response data from near field measurements. Pressure response data at a specified frequency is obtained from a near field linear array. Helmholtz integral relations for the enclosing sphere and integrals of the free-space Green’s function and its gradient for defined near field point locations are used along with physical assumptions to form an overdetermined system. The overdetermined system is solved via least squares yielding values of pressure and velocity corresponding to defined locations on the enclosing sphere. The enclosing sphere’s values of pressures and velocities are then used with integrals of the free-space Green’s function and its gradient to calculate far field response.

191 pages, Kindle Edition

First published March 4, 2012