Claims
- 1. Material for providing acoustic protection against a source of noise whose spectrum includes frequency components that are harmonically unrelated, the material comprising a flexible substrate having a surface, and a plurality of resonators formed on and extending substantially along said substrate surface, wherein each of said resonators has a characteristic predetermined resonant frequency, at which resonant frequency sound pressure from said noise source is absorbed and dissipated as energy, wherein said material attenuates harmonically related and harmonically unrelated frequency components present in said noise source.
- 2. Material according to claim 1, wherein said substrate defines a plurality of orifices having edges, at least some of said resonators being secured to said edges.
- 3. A material according to claim 1, wherein at least one said resonator includes a metallic membrane, and wherein said substrate includes an elastomeric material.
- 4. A material according to claim 1, wherein at least one said resonator is a composite membrane including at least two sheets of material having a high modulus of elasticity and a low damping factor, and a sheet of material having a low shear modulus and a high damping factor.
- 5. A material according to claim 4, wherein said composite membrane includes first and second sheets of a material having a high modulus of elasticity and a low damping factor, disposed on either side of a third sheet of material having a low shear modulus and a high damping factor.
- 6. A material according to claim 5, wherein said first and second sheets of material have a thickness in the range 10 microns to 200 microns and are selected from the group consisting of a metal and a metal alloy, and wherein said third sheet of material includes elastomer material having a thickness in the range 20 microns to 500 microns, and having a damping factor in the range 0.01 to 0.50.
- 7. A material according to claim 4, wherein said composite membrane includes first and second sheets of an elastomer material having low shear modulus and a high damping factor, disposed on either side of a third sheet of material having a high modulus of elasticity and a low damping factor selected from the group consisting of metal and a metal alloy.
- 8. A material according to claim 1, wherein at least one said resonator includes a membrane defining an outline shape selected from the group consisting of a circle, an ellipse, a crescent, a square, and a lobe.
- 9. A material according to claim 8, wherein each said membrane includes a lobe having end edges, and is secured to said substrate by said end edges.
- 10. A material according to claim 8, wherein said membrane includes corrugations and wherein said resonant frequency is determined by forming at least one array of said corrugations.
- 11. A material according to claim 8, wherein said membrane surface defines openings and wherein said resonant frequency is determined by a characteristic of said openings selected from the group consisting of opening shape and size.
- 12. A material according to claim 1, wherein said resonators include thread-like elements having a high modulus of elasticity, which elements are twisted together.
- 13. An acoustic protection material according to claim 1, wherein said resonators include vibrating blades having one blade end secured to said substrate, said blades having a high modulus of elasticity and include a material selected from the group consisting of metal and a polymer.
- 14. An acoustic protection material according to claim 1, wherein said resonators include composite vibrating blades having a high modulus of elasticity and include a material selected from the group consisting of metal, a polymer, and a material having a high damping factor.
- 15. Material according to claim 1, wherein said predetermined resonant frequency is determined by at least one characteristic of each said resonator selected from the group consisting of resonator density, resonator modulus of elasticity, resonator shear modulus, resonator damping factor, resonator piezoelectric characteristic, resonator size and resonator shape.
- 16. Material according to claim 1, wherein said energy is dissipated in an energy form selected from the group consisting of mechanical heat, and electrical energy.
- 17. Material according to claim 2, wherein at least one of said resonators has a form selected from the group consisting of a vibrating membrane, a vibrating blade, and a vibrating string.
- 18. Material for providing acoustic protection against a source of noise, the material comprising:
- a substrate including an elastomeric material and having a surface; and
- a plurality of resonators formed on and extending substantially along said substrate surface, at least one of said plurality of resonators being a composite membrane having at least one characteristic selected from the group consisting of:
- (a) a said composite membrane including at least two sheets of material having a high modulus of elasticity and a low damping factor, and a sheet of material having a low shear modulus and a high damping factor;
- (b) a said composite membrane including first and second sheets of a material having a high modulus of elasticity and a low damping factor, disposed on either side of a third sheet of material having a low shear modulus and a high damping factor;
- (c) a said composite membrane including first and second sheets of a material including a metal and having a high modulus of elasticity, a low damping factor, and a thickness in the range of 10 microns to 200 microns, said first and second sheets disposed on either side of a third sheet of material including an elastomer and having a low shear modulus, a damping factor in the range 0.01 to 0.50, and having a thickness in the range 20 microns to 500 microns; and
- (d) a said composite membrane including first and second sheets of an elastomer material having low shear modulus and a high damping factor, disposed on either side of a third sheet of material including a metal having a high modulus of elasticity and a low damping factor;
- wherein each of said resonators has a characteristic predetermined resonant frequency at which resonant frequency sound pressure from said noise source is absorbed and dissipated as energy.
- 19. Material for providing acoustic protection against a source of noise, the material comprising:
- a substrate having a surface; and
- a plurality of resonators, at least one of which resonators includes a membrane defining an outline shape selected from the group consisting of a circle, an ellipse, a crescent, a square, and a lobe, said resonators being formed on and extending substantially along said substrate surface;
- wherein each of said resonators has a characteristic predetermined resonant frequency at which resonant frequency sound pressure from said noise source is absorbed and dissipated as energy.
- 20. A material according to claim 14, wherein said membrane includes at least one characteristic selected from the group consisting of:
- (a) a said membrane including a lobe having end edges, wherein said membrane is secured to said substrate by said end edges;
- (b) a said membrane including corrugations, wherein said resonant frequency is determined by forming at least one array of said corrugations; and
- (c) a said membrane having a surface defining openings, wherein said resonant frequency is determined by a characteristic of said openings selected from the group consisting of opening shape and size.
Priority Claims (1)
Number |
Date |
Country |
Kind |
91 05104 |
Apr 1991 |
FRX |
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Parent Case Info
This is a continuing application of U.S. application Ser. No. 07/862,303, filed Apr. 2, 1992, pending.
US Referenced Citations (7)
Foreign Referenced Citations (6)
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Nov 1982 |
EPX |
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Non-Patent Literature Citations (1)
Entry |
Soviet Physics Acoustics, vol. 28, No. 4., 286-287, E. K. Grishchenko, et al. |
Continuations (1)
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Number |
Date |
Country |
Parent |
862303 |
Apr 1992 |
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