Acoustic and vibrational energy absorption metamaterials

An acoustic/vibrational energy absorption metamaterial comprising:

• an enclosed planar frame;
• a flexible membrane attached to said frame;
• at least one rigid platelet attached to said flexible membrane, the rigid platelet having an asymmetric shape, with a substantially straight edge at the attachment to said flexible membrane, the rigid platelet establishing a cell comprising a predetermined mass;
• and
• the rigid platelet mounted to provide a restoring force exerting by the flexible membrane upon displacement of the rigid platelet,
• wherein vibrational motions of the structure contain plural resonant modes with tunable resonant frequencies.

An acoustic/vibrational energy absorption metamaterial comprising:

• an enclosed planar frame;
• an flexible membrane attached to said frame;
• at least one rigid platelet attached to said flexible membrane with a frictional hinge attachment;
• the rigid platelet having an asymmetric shape, with a substantially straight edge at the attachment to said flexible membrane, the rigid platelet establishing a cell comprising a predetermined mass;
• and
• the rigid platelet mounted to provide a restoring force exerting by the flexible membrane upon displacement of the rigid platelet,
• wherein vibrational motions of the structure comprise plural resonant modes with tunable resonant frequencies, the vibrational motions of the structure containing a number of resonant modes with tunable resonant frequencies while using the frictional hinge attachment to absorb the vibration energy by replacing energy from movement of the rigid platelets by rotational torque and its amplified force density inside the hinge.