Three kinds of calculation methods to estimate easily the sound directivity in the plane perpendicular to the principal axis of a cylindrical housing, which represents a vibrating housing of planetary gearing, are provided and experimentally verified. One method is to apply the theoretical solution of the sound field produced by a point source placed on a sphere which replaces the housing of the same radius. The other two methods are based on an approximation in which point sources are placed on several infinite baffles attached to the cylinder surface. The former one gives very good estimation for the radiation. The latter two methods, causing irregular deviations in the resultant directivity, can be used sufficiently as the simplest way of calculation.