IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0720935
(1985-04-08)
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우선권정보 |
FR-0005558 (1984-04-09) |
발명자
/ 주소 |
|
출원인 / 주소 |
|
대리인 / 주소 |
Sughrue, Mion, Zinn, Macpeak & Seas
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인용정보 |
피인용 횟수 :
11 인용 특허 :
2 |
초록
▼
In sound absorbing lining, conduits (4) are provided, filled with a viscous damping fluid, and are in contact by their ends facing towards the rigid supporting wall (1) to which the lining is applied with flexible cells containing a gas and forming a readily compressible material, for example foam r
In sound absorbing lining, conduits (4) are provided, filled with a viscous damping fluid, and are in contact by their ends facing towards the rigid supporting wall (1) to which the lining is applied with flexible cells containing a gas and forming a readily compressible material, for example foam rubber (6). Said conduits are separated from the ambient medium (2) by a separating membrane (3) which is permeable to acoustic waves. Lining is applied to absorbing acoustic waves underwater.
대표청구항
▼
1. A sound absorbing wall lining having an inside surface adapted to be applied to a rigid supporting wall and an outside surface adapted to be steeped in a fluid environment, especially a liquid, traversed by acoustic waves, said lining comprising additional walls extending in a perpendicular direc
1. A sound absorbing wall lining having an inside surface adapted to be applied to a rigid supporting wall and an outside surface adapted to be steeped in a fluid environment, especially a liquid, traversed by acoustic waves, said lining comprising additional walls extending in a perpendicular direction from the supporting wall and forming therebetween a number of energy dissipating conduits in which an attenuating or dissipating fluid can move in a slight reciprocating motion normal to the supporting wall with a certain amount of friction, said conduits being substantially straight, with constant cross sections, and with openings at said outside surface and said inside surface, said lining further comprising a separating layer covering the outside openings of said conduits, which is permeable to acoustic waves, said lining wherein said energy dissipating conduits are filled with a dissipating fluid having a higher kinematic viscosity than the ambient fluid so that it may absorb, by laminar friction, the energy of said reciprocation motions, said separating layer being a membrane closing off the openings of the conduits to prevent the dissipating fluid from becoming diluted in the ambient fluid, said membrane being permeable to acoustic waves, and resilient, closed compression volumes being placed at the back of said conduits, in contact with the dissipating fluid, said volumes containing fluid more readily compressible than the ambient and the dissipating fluids such as to amplify said reciprocating motions of the latter fluid in response to incident acoustic waves. 2. A lining according to claim 1, wherein an equivalent hydraulic diameter d and length l of the energy dissipating conduits, a perforation rate S2/S1 of the lining at a level of said conduits and a density ρ 1 of the dissipating fluid are such as to substantially satisfy the equation: ##EQU##32(ρ 1 ·v 1 ·/d 2 )1=ρ o ·C o (S2/S1) where ρ o and C o stand respectively for the density of the ambient fluid and the velocity of acoustic waves in said fluid, such that there is a tuning frequency (f o ) for which matched frequency acoustic waves are virtually completely absorbed. 3. A lining according to claim 2, tuned to absorb waves at a frequency of less than about 1000 or 2000 Hz, said lining wherein the kinematic viscosity v 1 of said dissipating fluid is great enough and the equivalent hydraulic diameter d is small enough for the ratio of v 1 to d 2 to be more than 2,500 rd/s, such that the range of frequencies effectively absorbed will be broadly extended on each side of said tuning frequency f o . 4. Lining according to claim 2 intended to absorb more particularly acoustic waves near a tuning frequency f o, wherein the kinematic viscosity v 1 of said dissipating fluid is greater than, or at least only slightly less than the product f o ·d 2 of said frequency times the square of the equivalent diameter d, so that the distribution of reciprocation speeds in the flow section of the dissipating conduit is comparable to that obtaining in a continuous, one-way laminar flow. 5. Lining according to claim 4, wherein said viscosity v 1 is greater than half said product f o ·d 2 . 6. Lining according to claim 4, wherein a stiffness K of said resilient compression volumes confronting said dissipating fluid is selected to be substantially ##EQU##K=50/f o 2 ·S2/ρ 1 ·1 such that said tuning frequency is equal to frequency f o, said stiffness K being the relation of a force to a motion, said force being a longitudinal force able to be applied to the back of a conduit by an acoustic wave, said motion being the longitudinal motion caused by said force and equal to the change in total volume of said compression volumes due to the action of said force, said change being divided by the cross section of the conduit. 7. Lining according to claim 1, applicable to a situation where the ambient fluid is a liquid, wherein said separating membrane is made of a material having a value of a product of ρ 2 ·C 2 equal to a product of ρ o ·C o value of the ambient fluid, said product being that of the material's density times the material's sound velocity, to ensure sufficient thickness for the membrane for it to withstand external agressions and hydrostatic pressure differentials. 8. Lining according to claim 6, applicable to a situation where the ambient fluid is a liquid, wherein said dissipating fluid is an auxiliary liquid and said more readily compressible fluid is a gas enclosed in flexible cells, the overall enclosed volume of said flexible cell or cells at the back of each dissipating conduit being selected to yield approximately said K-value of stiffness. 9. Lining according to claim 8, wherein said dissipating fluid is made up of water with long-chain organic molecules added to enhance its viscosity. 10. Lining according to claim 8, wherein said gas is enclosed in said flexible cells at a swelling pressure greater than atmospheric pressure to prevent undue volume shrinkage of said cells when the surrounding hydraulic pressure increases. 11. Lining according to claim 1, wherein said dissipating conduits have an equivalent hydraulic diameter of less than 10 mm and more than 1 mm.
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