  Acoustic cloaks derived by coordinate transformation have opened up a new
field of considerable interest in the last two decades. However, since perfect
omnidirectional acoustic cloak relies on inhomogeneous and anisotropic
materials that posses extreme values in certain regions, this cloak was deemed
impossible to be attained even with metamaterials. Recently, our group was
competent to introduce a new kind of extreme acoustic material, named as
acoustic null medium (ANM), for attaining various devices. In this letter, an
extreme mapping function is exploited to achieve an omnidirectional acoustic
cloak. The attained extreme homogeneous material through this transformation
becomes ANM that can satisfy the extreme parameters requirement and as a
result, can hide the object from any incident acoustic waves. Several numerical
simulations were carried out to demonstrate the capability of the propounded
cloak in cloaking objects from sound fields. The propounded work will pave the
way towards cloaking arbitrary objects from any incident angle and obviate the
conventional challenges regarding this device.
