The realization of a near-frequency-independent acoustic metamaterial and the successful application of this material as a convex acoustic lens are introduced. The authors design a face-centered-orifice-cubic (FCOC) unit cell that has the characteristics of an acoustic wave retarder. The increment in the acoustic refractive index produced by the FCOC unit cell is observed by reducing the size of the orifice. Also the refractive index remains nearly constant with frequency increments in the frequency regime that satisfies the homogeneous medium condition of the metamaterial. Using these unit cells, the authors create a 2-dimensional acoustic metamaterial convex lens that correspond to the conventional optical convex lens and show that this lens focuses acoustic waves in the same manner that an optical lens focuses light waves. (c) 2015 American Institute of Physics.