EP0897176A1 - Unterwasserschallabsorber - Google Patents

Unterwasserschallabsorber Download PDF

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Publication number
EP0897176A1
EP0897176A1 EP98401927A EP98401927A EP0897176A1 EP 0897176 A1 EP0897176 A1 EP 0897176A1 EP 98401927 A EP98401927 A EP 98401927A EP 98401927 A EP98401927 A EP 98401927A EP 0897176 A1 EP0897176 A1 EP 0897176A1
Authority
EP
European Patent Office
Prior art keywords
cells
absorber
membrane
absorber according
compliant
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.)
Granted
Application number
EP98401927A
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English (en)
French (fr)
Other versions
EP0897176B1 (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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Publication of EP0897176A1 publication Critical patent/EP0897176A1/de
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Classifications

    • 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 we want to protect against the sonar detection, this is removed, or at least attenuated strongly, sonar echoes from this submarine.
  • the frequency of the received signals must be lower to a value which is inversely proportional to the cross section of ducts forming the honeycomb cells.
  • an acoustic 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 adjoining second 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 of the cells on the outside 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 liaising with 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.
  • 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 diaphragm 205, preventing it from coming under pressure apply against the external 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.
  • 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 function of the frequency, on the one hand of the example of the realization according to 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 to fix the membrane on it, by gluing for example, 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 has particularly significant and interesting improvements over a known absorber, with respect to anechoic performance and also the behavior under pressure and the ease of manufacture.

Landscapes

  • 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)
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 true EP0897176A1 (de) 1999-02-17
EP0897176B1 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)

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

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2818421A1 (fr) * 2000-12-20 2002-06-21 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

Citations (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
EP0161458A1 (de) * 1984-04-09 1985-11-21 Alsthom Akustische Wellen dämpfende Wandbedeckung
FR2586849A2 (fr) * 1985-05-31 1987-03-06 Vibrasonic Dispositif destine a absorber les ondes sonores.
US4817757A (en) * 1987-05-25 1989-04-04 Alsthom Wall covering for absorbing sound waves in a liquid medium
FR2656718A1 (fr) * 1989-12-28 1991-07-05 Thomson Csf Absorbeur acoustique pour milieu fluide, notamment pour milieu marin.
EP0509166A1 (de) * 1989-10-26 1992-10-21 Rohr Industries, Inc. Lärmdämpfende Wabenstruktur
EP0817164A1 (de) * 1996-06-28 1998-01-07 Bertin & Cie Geräuschabsorbierende Strukturen und daraus hergestellte Wände

Patent Citations (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
EP0161458A1 (de) * 1984-04-09 1985-11-21 Alsthom Akustische Wellen dämpfende Wandbedeckung
FR2586849A2 (fr) * 1985-05-31 1987-03-06 Vibrasonic Dispositif destine a absorber les ondes sonores.
US4817757A (en) * 1987-05-25 1989-04-04 Alsthom Wall covering for absorbing sound waves in a liquid medium
EP0509166A1 (de) * 1989-10-26 1992-10-21 Rohr Industries, Inc. Lärmdämpfende Wabenstruktur
FR2656718A1 (fr) * 1989-12-28 1991-07-05 Thomson Csf Absorbeur acoustique pour milieu fluide, notamment pour milieu marin.
EP0817164A1 (de) * 1996-06-28 1998-01-07 Bertin & Cie Geräuschabsorbierende Strukturen und daraus hergestellte Wände

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2818421A1 (fr) * 2000-12-20 2002-06-21 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

Also Published As

Publication number Publication date
DE69819426D1 (de) 2003-12-11
FR2767410B1 (fr) 1999-10-29
EP0897176B1 (de) 2003-11-05
FR2767410A1 (fr) 1999-02-19
DE69819426T2 (de) 2004-09-09

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