An external acoustic cloak with N-sided regular polygonal cross section based on complementary medium

The acoustic cloak is an important device, which can cloak an object from the detecting of sonar. Based on the concepts of complementary media and nonlinear coordination transformation, the generalized expressions for material parameters of the complementary medium-assisted external acoustic cloak with N-sided regular polygonal cross section are derived. It can cloak the object with arbitrary shape outside the cloaking domain, as long as an “antiobject” is embedded in the complementary layer. The external cloaking effect has been verified by full-wave simulation.