Acoustic and vibrational energy absorption metamaterials

Patent metadata

Field	Value
Publication number	US-9520121-B2
Application number	US-201414892213-A
Country	US
Kind code	B2
Filing date	May 27, 2014
Priority date	Jun 25, 2013
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

Abstract

A substantially acoustically transparent planar, rigid frame divided into a plurality of individual, substantially two-dimensional cells is used to construct a sound absorption panel. A sheet of a flexible material is fixed to the rigid frame, and a plurality of platelets fixed to the sheet of flexible material such that each cell is provided with a respective platelet, thereby establishing a resonant frequency, establishing an increase in an absorption coefficient of the panel. The flexible material has a wrinkle or corrugation to permit distortion with reduced material elasticity. The wrinkle or corrugation permits the flexible material to distort beyond that afforded by a planar material of the same type, while retaining mechanical strength in supporting the plurality of platelets.

First claim

What is claimed is:

1. A sound absorption panel comprising:
a substantially acoustically transparent planar, rigid frame divided into a plurality of individual, substantially two-dimensional cells;
a sheet of a flexible material fixed to the rigid frame, and a plurality of platelets fixed to the sheet of flexible material such that each cell is provided with a respective platelet, thereby establishing a resonant frequency, the resonant frequency defined by the planar geometry of the respective individual cells, the flexibility of the flexible material and said respective platelet thereon and establishing an increase in an absorption coefficient of the panel;
the cells comprising rigid platelets, wherein the rigid platelets have a flapping mode providing a tunable function; and
the flexible material having a wrinkle or corrugation to permit distortion with reduced material elasticity, thereby permitting the flexible material to distort beyond that afforded by a planar material of the same type, while retaining mechanical strength in supporting the plurality of platelets.

2. The sound absorption panel of claim 1 , wherein the wrinkle or corrugation of the sheets results in the resonant frequencies of the cells by lowering the resonant frequencies as compared to that achieved by the use of flat membrane of the same material.

3. The sound absorption panel of claim 1 , wherein the thickness of the sheet of solid materials varies across the cell.

4. The sound absorption panel of claim 1 , further comprising:
multiple layers of said solid material.

5. The sound absorption panel of claim 1 , further comprising:
a plurality of panels stacked together wherein each said panel comprises a rigid frame divided into a plurality of individual cells, a sheet of a solid material, and a plurality of platelets, with each platelet fixed to said sheet of solid material to provide each cell with a respective platelet; and
a working frequency of the sound absorption structure defined by the planar geometry of the individual cells, the flexibility of said solid material, and said respective platelet thereon.

6. The sound absorption panel of claim 5 , further comprising:
each said panel formed with platelets having different weights from other said panels in the panel.

7. The sound absorption panel of claim 1 , further comprising:
adjacent frames facing each other with a distance having a predetermined relationship to the size of said frames.

8. The sound absorption panel of claim 1 , wherein the flapping mode provides the tunable function whereby the frequency decreases in an approximate relationship to the inverse square root of the mass of platelets.

9. The sound absorption panel of claim 1 , wherein the flapping mode provides the tunable function whereby the flapping mode provides a tunable function based on the tunable resonant frequencies, said resonant frequencies tunable by varying the distance of separation between asymmetric platelets, or the thickness, elasticity, such as the Young's module and the Poisson ratio, and the wrinkle patterns of the membrane, the mass of the platelets, and the cell dimension.

10. The sound absorption panel of claim 1 , further comprising:
a plurality of platelets in each unit cell.

11. The sound absorption panel of claim 1 , further comprising:
the cells forming structural units comprising masses subject to vibratory motion and the vibratory motion has resonant frequencies that increases or decreases by varying the lateral dimensions of the structural units, the membrane elasticity and wrinkle patterns, and the material type and dimension of the platelets, thereby permitting selection of the resonant frequency as a lossy core.

12. 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;
the rigid platelet mounted to provide a restoring force exerting by the flexible membrane upon displacement of the rigid platelet; and
the cells comprising rigid platelets, wherein the rigid platelets have a flapping mode providing a tunable function,
wherein vibrational motions of the structure contain plural resonant modes with tunable resonant frequencies.

13. The acoustic/vibrational energy absorption metamaterial of claim 12 , further comprising a plurality of platelets in each unit cell.

14. The acoustic/vibrational energy absorption metamaterial of claim 13 , wherein adjacent frames face each other with a distance having a predetermined relationship to the size of said frames.

15. The acoustic/vibrational energy absorption metamaterial of claim 13 , wherein the flapping mode provides the tunable function whereby the frequency decreases in an approximate relationship to the inverse square root of the mass of platelets.

16. The acoustic/vibrational energy absorption metamaterial of claim 13 , wherein the flapping mode provides the tunable function based on the tunable resonant frequencies, said resonant frequencies tunable by varying the distance of separation between asymmetric platelets, or the thickness and elasticity of the membrane, the mass of the platelets, and the cell dimension.

17. The acoustic/vibrational energy absorption metamaterial of claim 16 , further comprising providing the tunable function by varying at least one of the Young's module and the Poisson ratio of the membrane.

18. The acoustic/vibrational energy absorption metamaterial of claim 13 , wherein the structural units comprise masses subject to vibratory motion and the vibratory motion has resonant frequencies that increases or decreases by varying the lateral dimensions of the structural units, a distance of separation between adjacent ones of the masses, the membrane thickness and elasticity, and the material type and dimension of the platelets, thereby permitting selection of the resonant frequency as a lossy core.

19. An acoustic/vibrational energy absorption metamaterial comprising:
a substantially acoustically transparent planar, rigid frame divided into a plurality of individual, substantially two-dimensional cells;
a sheet of a flexible material fixed to the rigid frame, and a plurality of platelets fixed to the sheet of flexible material such that each cell is provided with a plurality of platelets, thereby establishing a resonant frequency, the resonant frequency defined by the planar geometry of the respective individual cells, the flexibility of the flexible material and said respective platelet thereon and establishing an increase in an absorption coefficient of the panel;
the flexible material having a wrinkle or corrugation to permit distortion with reduced material elasticity, thereby permitting the flexible material to distort beyond that afforded by a planar material of the same type, while retaining mechanical strength in supporting the plurality of platelets; and
at least one aluminum reflector at a predetermined near-field distance behind the membrane, the aluminum reflector improving sound absorption.

20. The acoustic/vibrational energy absorption metamaterial of claim 12 , wherein
the vibrational motions of the structure contain a number of resonant modes with tunable resonant frequencies while using a frictional hinge attachment biased toward a neutral posit

Assignees

• Univ Hong Kong Science & Tech

Inventors

• Sheng Ping
• Yang Zhiyu
• Yang Min
• Sun Liang
• Ma Guancong
• Xiao Songwen

Classifications

• B32B2255/205

  Metallic coating · CPC title

• B32B2607/00

  Walls, panels · CPC title

• G10K11/172 Primary

  using resonance effects · CPC title

• B32B2307/102

  Insulating · CPC title

• G10K11/20

  Reflecting arrangements (G10K11/28 takes precedence) · CPC title