  The inverse acoustic scattering of point objects using multi-frequency sparse
measurements are studied. The objects may be a sum of point sources or point
like scatterers. We show that the locations and scattering strengths of the
point objects can be uniquely identified by the multi-frequency near or far
fields taken at sparse sensors. Based on the uniqueness analysis, some direct
methods have also been proposed for reconstructing the locations and
determining the scattering strengths. The numerical examples are conducted to
show the validity and robustness of the proposed numerical methods.
