The prediction of acoustic scattering requires the acoustic velocity evaluation on the scattering surface in order to satisfy the boundary conditions. According to the idea of acoustic analogy, this paper induces a vector wave equation of aeroacoustics by rearranging the conversation equations of mass and momentum with a penetrable surface. Then, an analytical formulation of the acoustic velocity, called formulation V2A, is derived for sources in a quiescent medium by solving the vector wave equation with the free-space Green’s function. The validity of the formulation is confirmed by numerical results for a stationary monopole, a stationary dipole source, and a rotating monopole source in quiescent medium. The result indicates that the predication of formulation V2A is identical to the exact solutions no matter in far-field or near-field.