Acoustic Radiation Fields of Axisymmetric Spherical Sources with Mixed Boundary Conditions.

摘要

Three acoustic radiation problems concerning axisymmetric radiating spheres with mixed boundary conditions on their surfaces have been treated numerically. They are:first, a radially vibrating polar cap mounted on an otherwise rigid spherical baffle;second,the same cap mounted on an otherwise pressure release spherical baffle;and third,the same cap and a contiguous pressure release belt,both mounted on an otherwise rigid spherical baffle. The solution of the first problem is obtainable in terms of eigenfunctions which are orthogonal over the sphere and is consequently well known;it was thus used as a comparison check for the second and third problem. The solutions of the above problems were accomplished by assuming a Fourier-Legendre series expansion of the acoustic pressure field and numerically determining the coefficients in the expansion,either by the least mean square error method,or by boundary collocation. The first and second problems were solved by both methods,while the third was treated by the least mean square error method only. The numerical computations were performed on an IBM 370/168digital computer in FORTRAN IV.