Sound field decomposition enables to estimate and interpolate an acoustic field inside a region including sources. Such a decomposition generally requires the discretization of a region of interest into a set of grid points to apply sparse representation algorithms. On the other hand, a gridless sound field decomposition method based on the reciprocity gap functional makes it possible to decompose it into point sources in a gridless manner with measurements on the boundary surface of the spherical target region. The closed-form algorithm is derived based on the reciprocity gap functional in the spherical harmonic domain with interpolating a sound field on the boundary. In this paper, further investigation on the interpolation methods for the gridless sound field decomposition is performed. The experimental results indicated that the highest accuracy is achieved by our proposed method, especially at high frequencies.
