Computationally optimized and manufactured acoustic metamaterials

Abstract

A system for fabricating an acoustic metamaterial is provided. In an embodiment, a system for fabricating an acoustic metamaterial includes determining at least one tuned physical property for each of a plurality of micro-resonators according to a desired acoustic property of the acoustic metamaterial. For a particular physical property, a value of the tuned physical property for at least one of the plurality of micro-resonators is different from a value of the tuned physical property for at least one other of the plurality of micro-resonators. The system also includes an additively manufacturing device configured to form the acoustic metamaterial such that the acoustic metamaterial comprises a first structure and the plurality of micro-resonators embedded within the first structure. Forming the acoustic metamaterial is performed such that an actual physical property of each of the plurality of micro-resonators is equal to a corresponding tuned physical property for each of the plurality of micro-resonators.

What is claimed is: 
     
         1 . A system for fabricating an acoustic metamaterial, comprising:
 a first data processing system configured to determine at least one of a desired mass density and a desired stiffness for each of a plurality of micro-resonators according to a desired acoustic property of the acoustic metamaterial, wherein at least one of a first condition and a second condition is satisfied, wherein first condition comprises the desired mass density of at least one of the plurality of micro-resonators is different from the desired mass density of at least one other of the plurality of micro-resonators and the second condition comprises the desired stiffness of at least one of the plurality of micro-resonators is different from the desired stiffness of at least one other of the plurality of micro-resonators; and   an additive manufacturing device configured to form the acoustic metamaterial such that the acoustic metamaterial comprises a first structure and the plurality of micro-resonators embedded within the first structure, depositing materials is performed such that at least one of an actual mass density of each of the plurality of micro-resonators is equal to a corresponding desired mass density and an actual stiffness of each of the plurality of micro-resonators is equal to a corresponding desired stiffness.   
     
     
         2 . The system of  claim 1 , further comprising:
 a second data processing system configured to determine a micro-resonator specific ratio of a first material and a second material such that a combination of the first material and the second material mixed according to the micro-resonator specific ratio has a material mass density equal to the desired mass density for a corresponding one of the plurality of micro-resonators.   
     
     
         3 . The system of  claim 2 , wherein the first data processing system comprises the second data processing system. 
     
     
         4 . The system of  claim 2 , wherein the additive manufacturing device is further configured to form each acoustic resonator from a mixture of a micro-resonator specific ratio of a first material and a second material such that a mass density of each micro-resonator is equal to the desired mass density for a corresponding one of the plurality of acoustic resonators, the first material comprising a first mass density, the second material comprising a second mass density different from the first mass density. 
     
     
         5 . The system of  claim 4 , wherein the additive manufacturing device is further configured to form a low mass density acoustic resonator from a one of the first and second materials having a lower mass density such that the low mass density acoustic resonator contains voids within the low mass density acoustic resonator such that a mass density of the low mass density acoustic resonator is less than a mass density of the first material one of the first and second materials having a lower mass density. 
     
     
         6 . The system of  claim 5 , wherein low mass density acoustic resonator comprises a ring of at least one of the first material and the second material, the ring defining a hole devoid of solid material, the combination of the ring and the hole providing a micro-resonator having a micro-resonator density equivalent to a corresponding desired mass density. 
     
     
         7 . The system of  claim 5 , wherein the voids comprise on of a gas, a vacuum, or another solid material. 
     
     
         8 . The system of  claim 6 , wherein the low mass density acoustic resonator further comprises a mesh structure within the hole. 
     
     
         9 . The system of  claim 2 , wherein the first material comprises tungsten (W) and the second material comprises a polymer. 
     
     
         10 . The system of  claim 5 , wherein the low mass density acoustic resonator comprises a porous foam like structure. 
     
     
         11 . The system of  claim 1 , wherein the desired acoustic property of the acoustic metamaterial comprises at least one of no vibrational wave propagation, acoustic dampening, structural isolation, and acoustic cloaking. 
     
     
         12 . The system of  claim 1 , wherein the desired acoustic property of the acoustic metamaterial comprises at least one of a negative modulus, a negative density, a negative refractive index, an imaginary speed of sound, a complex wave number, and a purely imaginary wave number.