  An alternative method is suggested for the description of the velocity and
pressure fields in an unbounded incompressible viscous fluid induced by an
arbitrary number of spheres moving and rotating in it. Within the framework of
this approach, we obtain the general relations for forces and torques exerted
by the fluid on the spheres. The behavior of the translational, rotational, and
coupled friction and mobility tensors in various frequency domains are analyzed
up to the terms of the third order in the dimensionless parameter equal to the
ratio of a typical radius of a sphere to the penetration depth of transverse
waves and a certain power of the dimensionless parameter equal to the ratio of
a typical radius of a sphere to the distance between the centers of two
spheres. We establish that the retardation effects can essentially affect the
character of the hydrodynamic interactions between the spheres.
