SOUND-PROPAGATION FROM A DIPOLE SOURCE NEAR AN IMPEDANCE PLANE

A closed-form analytic solution has been derived for an arbitrarily or iented dipole placed above an impedance plane. Asymptotic approximatio ns for the total sound field can be written in a form similar to the c lassical formula for a monopole. Analytic approximations derived for h orizontal and vertical dipoles give predictions that agree well with t hose obtained from a program of the fast field type. The asymptotic re sults have been confirmed also by laboratory measurements. Compared wi th numerical methods, the analytic approximations offer the combined a dvantages of easier physical interpretation and a much reduced computa tional time. It is found that the variation of the sound-pressure leve l from a vertical dipole above an impedance plane differs significantl y from that due to a monopole above this plane, particularly as a resu lt of differences in the ground wave component. However, the excess at tenuation due to a horizontal dipole is found to be rather similar to that for a monopole except for source and receiver heights that are co mparable with range. (C) 1997 Acoustical Society of America.