EP0897176B1 - Unterwasserschallabsorber - Google Patents

Unterwasserschallabsorber Download PDF

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Publication number
EP0897176B1
EP0897176B1 EP19980401927 EP98401927A EP0897176B1 EP 0897176 B1 EP0897176 B1 EP 0897176B1 EP 19980401927 EP19980401927 EP 19980401927 EP 98401927 A EP98401927 A EP 98401927A EP 0897176 B1 EP0897176 B1 EP 0897176B1
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EP
European Patent Office
Prior art keywords
cells
absorber
assembly
membrane
compliant material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19980401927
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English (en)
French (fr)
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EP0897176A1 (de
Inventor
Daniel Andreis
Michel Lagier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales Underwater Systems SAS
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Thales Underwater Systems SAS
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Publication date
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects

Definitions

  • the present invention relates to sound absorbers submarines which absorb the acoustic waves emitted by example by sonar. By placing such absorbers in front of an object, a submarine for example, which one wishes to protect against the sonar detection, this is removed, or at least attenuated strongly, sonar echoes from this submarine.
  • the frequency of the signals received must be lower to a value which is inversely proportional to the cross section of ducts forming the honeycomb cells.
  • a sound absorber can be submerged at depths of the order of 200 to 300 meters, corresponding to pressures of 20 to 30 bars, and successive of absorbing acoustic waves significantly in a wide low band frequency, typically between 0.5 Khz and 5 Khz.
  • the invention provides an absorber underwater acoustics, of the type comprising a first set of first adjoining cells, a viscous fluid filling these cells, a compliant material placed at one end of the cells, and a elastic membrane placed at the other end of these cells, mainly characterized in that it further comprises at least one second set of second contiguous cells, of larger diameter larger than that of the cells of the first set, filled with viscous fluid and located between said other end of the first cells and said elastic membrane.
  • the diameter of the first cells allows under the effect of the acoustic waves to be absorbed to make circulate the viscous fluid inside of them in a regime of Poiseuille at high frequency, and the diameter of the second cells support the elastic membrane without it stiffness which disrupts the operation of the absorber.
  • the compliant material constitutes a layer placed against said end from outside cells of it.
  • the compliant material is placed inside the cells.
  • the first set of first cells is divided into subsets each arranged at the interior of one of the second cells of the second set and the compliant material is placed inside said second cells in leaving a free space between the sub-assemblies and itself.
  • the second cells of the second set are made separately with their sub sets and their compliant materials to be then assembled together to form the second set.
  • a honeycomb structure comprising a set of cells contiguous 102 oriented towards the direction from which the acoustic waves arrive to absorb. Inside each cell is filled with a viscous liquid 103 resting on a compressible volume 104 generally composed of a compliant material such as plastic foam.
  • This compliant material itself rests on the support 101 in ensuring the connection with the structure 102.
  • the front face directed towards the arrival of the acoustic waves is closed by a flexible membrane 105 which isolates the cells from the contact of the water .
  • the acoustic wave attenuation performance of such device can be characterized from the modulus of the coefficient of reflection R as a function of frequency.
  • each cell represents a mass / spring system whose mass is constituted by that of the viscous fluid and the spring by the compliant material and whose reaction to the acoustic wave is considered to be being pure stiffness.
  • S is the section of the cell l is the height of the fluid
  • M is the plate module of the compliant material
  • e is the thickness of this compliant material
  • ⁇ is the viscosity of the fluid
  • ⁇ is the density of the fluid
  • ⁇ is the pulsation of the acoustic wave to be absorbed.
  • the first solution can hardly be applied, except in very specific cases, since the low cut-off frequency fc from which the anechoic phenomenon appears is proportional to the stiffness, while the resonance frequency f r is proportional to the square root of this stiffness. By thus increasing the value of the stiffness, one would shift the low threshold of the useful band more towards the high frequencies than its high ceiling and one would decrease the useful bandwidth.
  • the minimum allowable radius for cells, below which the effect of the closing membrane is too important, is of the order of 2 mm, which corresponds to the example of realization described above.
  • the invention proposes to use a structure such as that shown in Figure 3.
  • the absorber which rests on a support rigid 201, comprises, as known in the prior art, a set of honeycomb cells 202 perpendicular to the support 201. These cells are filled with a suitable viscous liquid 203 and are based on a layer of compressible foam 204 located between the nest structure and the support 201.
  • the fact that the foam 204 forms a layer continuous instead of being inserted into the bottom of the cells is a variant known in itself and which facilitates the construction of the device without deteriorate its performance.
  • the dimensions of the cells are chosen to obtain the desired frequency results, for example using the calculation method described above.
  • the fluid that fills the cells usually an oil relatively thick, although viscous is sufficiently fluid to flow outside of these cells if not retained by a means adequate.
  • the invention proposes to use a second honeycomb structure formed of significantly larger 206 cells larger than cells 202 and which is superimposed on the first structure.
  • These cells are filled with the same fluid 203 as that which filled cells 202 and they are closed by an elastic membrane 205 located at the front and which isolates them from the liquid medium in which the absorber is immersed.
  • the size of these 206 cells can be significantly larger larger than that of cells 202, since they only serve to support the membrane 205 by preventing it from coming under pressure apply against the exterior opening of these cells 202.
  • the stiffness provided by the membrane 205 can be overlooked.
  • the acoustic waves then pass through it and set the liquid in motion in cells 206, producing a some absorption of these waves for very low frequencies.
  • the movement of the liquid inside the 206 cells is then communicated to the liquid inside cells 202 and most of the desired absorption occurs inside these same cells.
  • FIG. 5 we uses a basic honeycomb structure formed from cells 506 to large section which rest directly on the rigid support 501 and are closed by a 505 membrane.
  • the absorbent structure itself is a honeycomb structure formed from subsets of cells 502 of small section which are inserted inside the cells 506.
  • a layer of compressible foam 504 is placed at the bottom of cells 506, leaving an empty space between cells 502 and itself.
  • Cells 502, and the empty spaces in cells 506 in before and behind these, are filled with a viscous liquid 503.
  • S 1 is the surface of the cross section of a cell. classical, l f its length, and e m1 the thickness of the compressible layer.
  • S2 is the surface of the cross section of the large cell, l 1 its thickness, Sc the surface of the cross section of small cells, l 2 its length, l 3 the distance between the base of the small cells and the front side of the foam layer, and e m2 the thickness of the layer 12.
  • n c is the number of cells 502 which is less than ⁇ because of the filling rate.
  • l 1 in the structure according to the invention l 1 must be dimensioned so as to allow the static deformation of the closing membrane when the coating is pressurized.
  • the ratio between the resonance frequencies f r according to (6) is equal to: l f l 1 + l 3 + ⁇ ⁇ l f
  • the ratio between the frequencies f p according to (7) is equal to: ⁇ ⁇
  • FIG. 6 shows the absorption curves in frequency function, on the one hand from the example of the realization according to the art known described above, which is identical to that of Figure 2, and other part of the embodiment of the invention, in order to compare the results of these two exemplary embodiments.
  • the large size of the cells on the front allows the membrane to be fixed thereon, for example by gluing, easier and more reliable way. Furthermore the decline in this membrane under the effect of static pressure is done on a larger length, so it's not critical.
  • the cell bottom material either a structural foam of the polyurethane type for example, or a composite material consisting for example of a dispersion of inclusions of air bubbles in an elastomeric matrix, of polyurethane type microinclusive for example.
  • the acoustic absorber according to the invention can also function as an acoustic barrier, that is to say in attenuating noise from the carrier vehicle on the support side rigid.
  • the absorber according to the invention exhibits particularly significant and interesting improvements over a known absorber, with regard to anechoic performance and also the behavior under pressure and the manufacturing facilities.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Combined Devices Of Dampers And Springs (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Claims (6)

  1. Unterwasser-Schalldämpfer des Typs, der eine erste Gruppe aus aneinandergrenzenden ersten Zellen (202), eine viskose Flüssigkeit (203), mit denen diese Zellen befüllt sind, ein elastisches Material (204), das an einem der Enden der Zellen angeordnet ist, und eine elastische Membran (205), die am anderen Ende dieser Zellen angeordnet ist, umfaßt, dadurch gekennzeichnet, daß er außerdem wenigstens eine zweite Gruppe zweiter aneinandergrenzender Zellen (206) mit einem Durchmesser, der größer als jener der Zellen der ersten Gruppe ist, umfaßt, die mit viskosem Fluid gefüllt ist und sich zwischen dem anderen Ende der ersten Zellen und der elastischen Membran befindet.
  2. Dämpfer nach Anspruch 1, dadurch gekennzeichnet, daß der Durchmesser der ersten Zellen (202) ermöglicht, unter der Wirkung der zu dämpfenden Schallwellen das viskose Fluid (203) in diesen in einem Hochfrequenz-Poiseuille-Bereich zirkulieren zu lassen, und daß der Durchmesser der zweiten Zellen (206) ermöglicht, die elastische Membran (205) zu unterstützen, ohne daß dies zu einer Steifigkeit führt, die die Funktion des Dämpfers stört.
  3. Dämpfer nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, daß das nachgiebige Material (204) eine Schicht bildet, die an dem Ende der Zellen außerhalb desselben angeordnet ist.
  4. Dämpfer nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, daß das nachgiebige Material (214) in den Zellen angeordnet ist.
  5. Dämpfer nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, daß die erste Gruppe erster Zellen in Untergruppeen (502) unterteilt ist, die jeweils in einer der zweiten Zellen der zweiten Gruppe angeordnet sind, und daß das nachgiebige Material (504) in den zweiten Zellen angeordnet ist, wobei zwischen den Untergruppen und ihm selbst ein Freiraum (503) vorhanden ist.
  6. Dämpfer nach Anspruch 5, dadurch gekennzeichnet, daß die zweiten Zellen der zweiten Gruppe mit ihren Untergruppen und nachgiebigen Materialien (504) in unterschiedlicher Weise gefertigt sind, um anschließend zusammengefügt zu werden, um die zweite Gruppe zu bilden.
EP19980401927 1997-08-14 1998-07-28 Unterwasserschallabsorber Expired - Lifetime EP0897176B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9710377A FR2767410B1 (fr) 1997-08-14 1997-08-14 Absorbeur acoustique sous-marin
FR9710377 1997-08-14

Publications (2)

Publication Number Publication Date
EP0897176A1 EP0897176A1 (de) 1999-02-17
EP0897176B1 true EP0897176B1 (de) 2003-11-05

Family

ID=9510307

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19980401927 Expired - Lifetime EP0897176B1 (de) 1997-08-14 1998-07-28 Unterwasserschallabsorber

Country Status (3)

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EP (1) EP0897176B1 (de)
DE (1) DE69819426T2 (de)
FR (1) FR2767410B1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2818421B1 (fr) * 2000-12-20 2003-03-28 Eads Airbus Sa Panneau acoustique sandwich a plusieurs degres de liberte
CN112164382A (zh) * 2020-09-07 2021-01-01 西安交通大学 一种曲折隔板填充粘弹性材料水下吸声结构

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3439774A (en) * 1966-01-21 1969-04-22 Boeing Co Sound energy absorbing apparatus
FR2562699B1 (fr) * 1984-04-09 1986-12-05 Alsthom Atlantique Revetement de paroi absorbant les ondes acoustiques
FR2586849B2 (fr) * 1985-05-31 1989-01-20 Vibrasonic Dispositif destine a absorber les ondes sonores.
FR2615994B1 (fr) * 1987-05-25 1989-07-28 Alsthom Revetement de paroi absorbant les ondes acoustiques en milieu liquide
US5041323A (en) * 1989-10-26 1991-08-20 Rohr Industries, Inc. Honeycomb noise attenuation structure
FR2656718A1 (fr) * 1989-12-28 1991-07-05 Thomson Csf Absorbeur acoustique pour milieu fluide, notamment pour milieu marin.
FR2750527B1 (fr) * 1996-06-28 1998-08-21 Bertin & Cie Structures d'absorption de bruit et parois constituees de ces structures

Also Published As

Publication number Publication date
FR2767410A1 (fr) 1999-02-19
DE69819426D1 (de) 2003-12-11
EP0897176A1 (de) 1999-02-17
DE69819426T2 (de) 2004-09-09
FR2767410B1 (fr) 1999-10-29

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