Weidlinger Associates Inc. proposes to continue the development of metamaterial-based acoustic cloaking technology, and proposes to formulate and manufacture prototype cloak materials and demonstrate their effectiveness through in-water acoustic scattering tests of cloaked cylindrical shells. The Subsequent Phase II Project will be implemented as a 12 18 month Base task followed by two Option tasks. In the base effort, success is defined as a satisfactory TRL 4 proof-of-concept demonstration. If continued, the two option tasks will culminate in successful design, manufacturing and laboratory water tank demonstration of a torpedo-sized prototype acoustic cloak. Specific objectives include: To mature the theory and practice of pentamode-based acoustic metamaterials, To design and manufacture prototype acoustic cloak materials, To conduct laboratory experiments to validate the design methods and acoustic scattering properties