  Isogeometric analysis with the boundary element method (IGABEM) has recently
gained interest. In this paper, the approximability of IGABEM on 3D acoustic
scattering problems will be investigated and a new improved BeTSSi submarine
will be presented as a benchmark example. Both Galerkin and collocation are
considered in combination with several boundary integral equations (BIE). In
addition to the conventional BIE, regularized versions of this BIE will be
considered. Moreover, the hyper-singular BIE and the Burton--Miller formulation
are also considered. A new adaptive integration routine is presented, and the
numerical examples show the importance of the integration procedure in the
boundary element method. The numerical examples also include comparison between
standard BEM and IGABEM, which again verifies the higher accuracy obtained from
the increased inter-element continuity of the spline basis functions. One of
the main objectives in this paper is benchmarking acoustic scattering problems,
and the method of manufactured solution will be used frequently in this regard.
