  This paper is concerned with the uniqueness of inverse acoustic scattering
problem for cavities with the modulus of the near-fields. With the aid of the
reference ball technique and the superpositions of two point sources as the
incident waves, we rigorously prove that the location and shape of the cavity
as well as its boundary condition can be uniquely determined by the modulus of
near-fields at an admissible surface. To our knowledge, this is the first
uniqueness result in inverse cavity scattering problems with phaseless
near-field data. In this paper, we make use of the phaseless near-field data
incurred by the cavity and the point sources, and thus the configuration is
more feasible in practice.
