This　paper　presents　a　novel　method　for　topology　optimization　of　vibrating　structures　interacted　with　acoustic　wave　for　the　purpose　of　minimizing　radiated　sound　power　level.　We　consider　exterior　acoustic　fields　and　bimaterial　shell　models　without　damping　in　this　work.　Within　the　isogeometric　analysis　framework,　we　employ　Catmull-Clark　subdivision　surfaces　to　construct　geometries　and　discretize　physical　fields.　The　isogeometric　finite　element　method　with　Kirchhoff-Love　shell　elements　is　coupled　with　the　isogeometric　boundary　element　method　in　acoustics.　The　topology　optimization　is　performed　through　density-based　approaches,　in　which　the　sensitivities　are　evaluated　with　adjoint　variable　methods.　Numerical　experiments　demonstrate　the　validity　and　effectiveness　of　the　algorithm　for　topology　optimization　of　structural-acoustic　interaction　systems.