ACOUSTIC RADIATION FROM A PAIR OF SPHERES

In this paper we present a semi-analytical model which enables the aco ustic pressure field created by two spheres radiating close together t o be predicted at any point outside the spheres. By representing the p ressure field from each sphere as a finite sum of spherical harmonics and satisfying the boundary conditions at a finite number of points on the surface of each sphere, the problem reduces to the solution of a system of simultaneous linear equations whose unknown variables are th e relative amplitudes of each spherical harmonic. The results from thi s model have been compared with those obtained using a boundary elemen t method approach. It is shown that for values of ka < 10 both methods give results with a relative error less than 1% for separated spheres . The case for contacting spheres is discussed and results presented. Numerical examples demonstrate the accuracy and convergence rates of t he two methods. A detailed analysis of the radiation problem when the spheres are in contact is given in an Appendix.