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EP0114764A2 - Interface device for acoustic wave reflection - Google Patents

Interface device for acoustic wave reflection Download PDF

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Publication number
EP0114764A2
EP0114764A2 EP84400076A EP84400076A EP0114764A2 EP 0114764 A2 EP0114764 A2 EP 0114764A2 EP 84400076 A EP84400076 A EP 84400076A EP 84400076 A EP84400076 A EP 84400076A EP 0114764 A2 EP0114764 A2 EP 0114764A2
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EP
European Patent Office
Prior art keywords
volume
wall
rigid wall
acoustic waves
rigid
Prior art date
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Granted
Application number
EP84400076A
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German (de)
French (fr)
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EP0114764B1 (en
EP0114764A3 (en
Inventor
Bernard Fromont
René Reynier
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Thales SA
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Thomson CSF SA
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Publication of EP0114764A3 publication Critical patent/EP0114764A3/en
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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
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/20—Reflecting arrangements
    • G10K11/205—Reflecting arrangements for underwater use

Definitions

  • the reflection of acoustic waves according to an interface separating two media of impedances Z 1 and Z 2 is linked to a ratio Z I / Z 2 different from unity.
  • the invention relates more particularly to devices with an acoustic wave reflector interface of the "soft" type.
  • reflectors are known, the structure of which is made of a flexible and waterproof envelope which contains two rigid plates enclosing an airy structure made of metal wires.
  • These reflectors have the drawback of losing their deformability too quickly when they have to withstand a high hydrostatic pressure which is encountered at immersion depths of a few tens of meters.
  • the reflective interface risks losing its shape and can change position relative to the transducers mounted nearby, so that the expected phase shifts are modified.
  • the main object of the invention is a device for reflecting acoustic waves according to an interface separating a volume of viscoelastic material with gas cells from a material permeable to said acoustic waves used to isolate this volume from the external fluid medium of higher density, characterized in that said volume is applied against a rigid wall made of said permeable material; said wall being carried by a rigid support; a flexible closing element cooperating with said rigid wall to ensure the tightness of said device while transmitting to said volume the external hydrostatic pressure, in order to prevent the deformation and the change of position of the interface whose shape is imposed by said wall rigid.
  • the reflection device of FIG. 1 comprises upstream of the reflective interface 24 a rigid wall 21 comprising a flange 28.
  • This wall which takes the form of an open housing is, permeable to acoustic waves while serving as a means of sealing against the external fluid.
  • the wall 21 is made of a material transparent to incident acoustic waves such as an organic synthetic material.
  • the open case 21 can for example be made up of an assembly of glass fibers impregnated with polyester resin. After polymerization, a resistant and light shell is obtained. It is also possible to use for the housing 21 a material of acoustic impedance markedly greater than poCo, for example metal, but the thickness must satisfy certain conditions for transmission of the incident acoustic waves.
  • the stiffness provided by the housing 21 is sufficient to prevent any deformation resulting from the action of the hydrostatic pressure.
  • the casing 30 can overflow so as to cover the rim (28) of the housing 21 to which it is fixed by means of an adhesive 23, contributing to the sealing of the assembly
  • the casing 30 can cover the entire reflecting device of the flexible closing element which undergoes all the deformations which result from the crushing of the foam by hydrostatic pressure, but the presence of gaseous cells prevents packing which would undesirably modify the acoustic impedance used for r effectively deflecting incident acoustic waves.
  • the foam 20 reflects the acoustic waves.
  • Figure 3 shows the device of Figure 1 subjected to external hydrostatic pressure.
  • the hydrostatic pressure, symbolized by the arrows 32 is exerted in particular on the faces 27 and 29 of the reflector.
  • the casing 30 fully transmits the pressure to the viscoelastic foam 20, which transmits it entirely to the rigid casing 21.
  • the pressures exerted on its two main faces being the same, the casing does not deform when the hydrostatic pressure varies.
  • the foam 20 of thickness d is crushed.
  • the thickness d e is chosen so that is weak compared to ⁇ 1 c 1 , at the lowest frequency that we want to reflect with the reflector.
  • Ci is the reduced thickness of the foam 20 at the maximum depth for which the device according to the invention is intended, so that the thickness d must be chosen accordingly.
  • FIG. 4 illustrates an alternative embodiment of the device according to the invention where the rigid wall 21 is a simple plate fixed directly to the structure 26 by means of a support forming a mounting frame 110. Openings 112 are provided in the frame 110 , so that the external hydrostatic pressure can act on the face 29 of the device.
  • the face 29 belongs to a flexible closing element which envelops the foam 20 and which is sealed against the wall 21.
  • a soft reflector device can be provided, for example, with a sheet of piezoelectric material 31 placed between electrodes to perform the transducer function on transmission or on reception. This variant is illustrated in FIG. 5.
  • the reflector devices described above are particularly well suited to the production of passive listening antennas which include one or more hydrophones.
  • the hydrophones are located opposite a reflecting surface composed of a set of devices as described above.
  • the shortest distance separating each hydrophone from the reflecting surface is advantageously equal to ⁇ / 4 where ⁇ is the wavelength corresponding to the central frequency of the listening band of the hydrophones.
  • FIG. 6 illustrates an example of arrangement of the reflectors 41 and hydrophones 40, in a passive listening antenna using a reflective surface of cylindrical shape.
  • the reflectors 41 have an elementary reflective surface of square shape and the hydrophones 40 are located directly above the center of symmetry of each elementary surface.
  • the reflectors 41 are held contiguously on a base by means of stirrups 42 held by tie rods 43, for example of steel.
  • Figure 7 is a sectional view of the device of Figure 6.
  • the base 26 of the antenna being for example cylindrical
  • the reflectors 41 are curved to match the structure and are held contiguously by means of stirrups 42 retained by steel tie rods 43 on the base 26.
  • Holes 45 allow the water to exert hydrostatic pressure on the faces 29 of the reflector devices according to the invention.
  • FIG. 8 illustrates an example of an arrangement similar to that of FIG. 6, but where the reflectors 41 are triangular. It is obvious that other arrangements of reflectors and hydrophones can be adopted without departing from the scope of the present invention.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

L'invention se rapporte aux dispositifs à réflexion d'ondes acoustiques dans une large bande de fréquences. L'invention a principalement pour objet un dispositif à réflexion d'ondes acoustiques du type mou comprenant un volume de mousse viscoélastique à alvéoles gazeuses (20) enveloppé par une paroi rigide (21) et par un élément souple de fermeture (29). L'invention s'applique notamment aux antennes sonar d'écoute passive.The invention relates to devices for reflecting acoustic waves in a wide frequency band. The main object of the invention is a device for reflecting acoustic waves of the soft type comprising a volume of viscoelastic foam with gas cells (20) enveloped by a rigid wall (21) and by a flexible closing element (29). The invention applies in particular to passive listening sonar antennas.

Description

La présente invention concerne des dispositifs à réflexion d'ondes acoustiques se propageant dans un fluide tel que l'eau.The present invention relates to devices for reflecting acoustic waves propagating in a fluid such as water.

La réflexion d'ondes acoustiques selon une interface séparant deux milieux d'impédances Z1 et Z2 est liée à un rapport ZI/Z2 différent de l'unité.The reflection of acoustic waves according to an interface separating two media of impedances Z 1 and Z 2 is linked to a ratio Z I / Z 2 different from unity.

Si les ondes à réfléchir se propagent dans un milieu d'impédance Z1 = ρ1 CI où p est la masse spécifique de la matière et C la célérité du son et si le milieu adjacent présente l'impédance Z2 = ρ2 C21 le rapport R de l'énergie acoustique réfléchie à l'énergie incidente est donné par la relation :

Figure imgb0001
If the waves to be reflected propagate in a medium of impedance Z 1 = ρ 1 CI where p is the specific mass of matter and C the speed of sound and if the adjacent medium has the impedance Z 2 = ρ 2 C 21 the ratio R of the reflected acoustic energy to the incident energy is given by the relation:
Figure imgb0001

Pour obtenir une forte réflexion, il faut que Zz soit très différent de Z1. Il existe donc deux types de réflecteurs d'ondes acoustiques: les réflecteurs "durs" dont l'impédance acoustique Z2 est supérieure à l'impédance Z1 de l'eau et les réflecteurs "mous" dont l'impédance acoustique Z2 est inférieure à l'impédance Z1de l'eau.To obtain a strong reflection, Z z must be very different from Z 1 . There are therefore two types of acoustic wave reflectors: "hard" reflectors whose acoustic impedance Z 2 is greater than the impedance Z 1 of water and "soft" reflectors whose acoustic impedance Z 2 is lower than the impedance Z 1 of the water.

L'invention concerne plus particulièrement des dispositifs à interface réflecteur d'ondes acoustiques du type "mou". Dans ce domaine, on connaît des réflecteurs dont la structure est faite d'une enveloppe souple et étanche qui renferme deux plaques rigides enserrant une structure aérée en fils métalliques. Ces réflecteurs présentent l'inconvénient de perdre trop rapidement leur déformabilité lorsque qu'ils ont à supporter une pression hydrostatique importante que l'on rencontre à des profondeurs d'immersion de quelques dizaines de mètres. En outre, l'interface réflectrice risque de perdre sa forme et peut changer de position par rapport aux transducteurs montés à proximité, de sorte que les déphasages escomptés sont modifiés.The invention relates more particularly to devices with an acoustic wave reflector interface of the "soft" type. In this field, reflectors are known, the structure of which is made of a flexible and waterproof envelope which contains two rigid plates enclosing an airy structure made of metal wires. These reflectors have the drawback of losing their deformability too quickly when they have to withstand a high hydrostatic pressure which is encountered at immersion depths of a few tens of meters. In addition, the reflective interface risks losing its shape and can change position relative to the transducers mounted nearby, so that the expected phase shifts are modified.

Dans le même ordre d'idée, on connaît des structures à réflexion d'onde mettant en oeuvre un coussin réflecteur en mousse qui présentent les mêmes inconvénients. La mousse utilisée a une densité inférieure à celle de l'eau et est constituée d'alvéoles gazeuses délimitées par une matrice en matériau viscoélastique du genre élastomère. Cette mousse résiste bien à la pression hydrostatique et conserve de bonnes propriétés réflectrices.In the same vein, wave reflection structures are known employing a foam reflective cushion which have the same drawbacks. The foam used has a density lower than that of water and consists of gaseous cells delimited by a matrix of viscoelastic material of the elastomer type. This foam resists well to hydrostatic pressure and retains good reflecting properties.

L'invention a principalement pour objet un dispositif à réflexion d'ondes acoustiques selon une interface séparant un volume de matériau viscoélastique à alvéoles gazeuses d'un matériau perméable auxdites ondes acoustiques servant à isoler ce volume du milieu fluide extérieur à densité supérieure, caractérisé en ce que ledit volume est appliqué contre une paroi rigide faite dudit matériau perméable ; ladite paroi étant portée par un support rigide ; un élément souple de fermeture coopérant avec ladite paroi rigide pour assurer l'étanchéité dudit dispositif tout en transmettant audit volume la pression hydrostatique extérieure, afin d'empêcher la déformation et le changement de position de l'interface dont la forme est imposée par ladite paroi rigide.The main object of the invention is a device for reflecting acoustic waves according to an interface separating a volume of viscoelastic material with gas cells from a material permeable to said acoustic waves used to isolate this volume from the external fluid medium of higher density, characterized in that said volume is applied against a rigid wall made of said permeable material; said wall being carried by a rigid support; a flexible closing element cooperating with said rigid wall to ensure the tightness of said device while transmitting to said volume the external hydrostatic pressure, in order to prevent the deformation and the change of position of the interface whose shape is imposed by said wall rigid.

L'invention sera mieux comprise au moyen de la description ci-après et des figures annexées données comme des exemples non limitatifs, parmi lesquelles :

  • - la figure 1 est une vue en coupe du dispositif à réflexion selon l'invention ;
  • - la figure 2 est une figure explicative ;
  • - la figure 3 montre le dispositif de la figure 1, subissant une pression hydrostatique ;
  • - la figure 4 est une vue en coupe d'une variante de dispositif selon l'invention ;
  • - la figure 5 est une variante de réalisation du dispositif selon l'invention ;
  • - la figure 6 est une vue partielle d'une antenne acoustique mettant e* oeuvre le dispositif selon l'invention ;
  • - la figure 7 est une vue en coupe partielle de l'antenne de la figure 6 ;
  • - la figure 8 illustre à titre de variante l'agencement triangulé de réflecteurs d'ondes placés à distance d'une nappe d'hydrophones.
The invention will be better understood by means of the description below and the appended figures given as nonlimiting examples, among which:
  • - Figure 1 is a sectional view of the reflection device according to the invention;
  • - Figure 2 is an explanatory figure;
  • - Figure 3 shows the device of Figure 1, undergoing hydrostatic pressure;
  • - Figure 4 is a sectional view of a variant device according to the invention;
  • - Figure 5 is an alternative embodiment of the device according to the invention;
  • - Figure 6 is a partial view of an acoustic antenna using the device according to the invention;
  • - Figure 7 is a partial sectional view of the antenna of Figure 6;
  • - Figure 8 illustrates as a variant the triangulated arrangement of wave reflectors placed at a distance from a sheet of hydrophones.

Sur la figure 1, l'on voit un dispositif à réflexion d'ondes acoustiques où l'incidence normale est représentée par la flèche X'X. Ce dispositif qui repose sur un support 26, comprend par exemple un volume 20 de mousse à alvéoles gazeuses faites d'un matériau viscoélastique ayant une densité moitié moindre que celle de l'eau. Le matériau viscoélastique est avantageusement constitué de polyuréthane, de caoutchouc synthétique, de chlorure de polyvinyle, ou d'acétate d'éthylène et de vinyle. (EVA).In Figure 1, we see a device for reflecting acoustic waves where the normal incidence is represented by the arrow X'X. This device, which rests on a support 26, comprises for example a volume 20 of foam with gas cells made of a viscoelastic material having a density half less than that of water. The viscoelastic material is advantageous suitably made of polyurethane, synthetic rubber, polyvinyl chloride, or ethylene and vinyl acetate. (EVA).

Le dispositif à réflexion de la figure 1 comprend en amont de l'interface réflectrice 24 une paroi rigide 21 comportant un rebord 28. Cette paroi qui épouse la forme d'un boîtier ouvert est, perméable aux ondes acoustiques tout en servant de moyen d'étanchéité vis-à-vis du fluide extérieur. La paroi 21 est réalisée dans une matière transparente aux ondes acoustiques incidentes telle qu'un matériau organique de synthèse. Le boîtier ouvert 21 peut par exemple être constitué d'un assemblage de fibres de verre imprégnées de résine polyester. Après polymérisation, on obtient une coque résistante et légère. On peut aussi utiliser pour le boîtier 21 une matière d'impédance acoustique nettement supérieure à poCo par exemple du métal, mais l'épaisseur doit satisfaire à certaines conditions de transmission des ondes acoustiques incidentes. Lorsque le boîtier 21 est métallique son épaisseur de paroi sera comprise entre quelques dixièmes de millimètre et quelques millimètres. Le boîtier 21 impose à la face .24 de la mousse 20 une forme précise qui ne doit pas se modifier sous l'action de la pression hydrostatique. La face externe 29 du dispositif à réflexion opposée à la face externe 27 de la paroi 21 est recouverte par une enveloppe 30 souple, par exemple en matériau élastomère de quelques millimètres d'épaisseur. Cet élément de fermeture complète l'étanchéité du dispositif tout en transmettant efficacement via la mousse 20, la pression hydrostatique qui se "trouve ainsi appliquée également sur les deux faces de la paroi du boîtier rigide 21. Comme la rigidité de l'élément souple de fermeture n'empêche pas la pression extérieure d'agir aussi à l'intérieur, la rigidité prppre du boîtier 21 est suffisante pour empêcher toute déformation résultant de l'action de la pression hydrostatique. L'enveloppe 30 peut déborder de manière à recouvrir le rebord (28) du boîtier 21 auquel elle est fixée au moyen d'un adhésif 23, participant à l'étanchéité de l'ensemble. Avantageusement, l'enveloppe 30 peut recouvrir tout le dispositif réflecteur de l'élément souple de fermeture qui subit toutes les déformations qui résultent de l'écrasement de la mousse par la pression hydrostatique, mais la présence d'alvéoles gazeuses empêche un tassement qui modifierait de façon indésirable l'impédance acoustique servant à réfléchir efficacement les ondes acoustiques incidentes.The reflection device of FIG. 1 comprises upstream of the reflective interface 24 a rigid wall 21 comprising a flange 28. This wall which takes the form of an open housing is, permeable to acoustic waves while serving as a means of sealing against the external fluid. The wall 21 is made of a material transparent to incident acoustic waves such as an organic synthetic material. The open case 21 can for example be made up of an assembly of glass fibers impregnated with polyester resin. After polymerization, a resistant and light shell is obtained. It is also possible to use for the housing 21 a material of acoustic impedance markedly greater than poCo, for example metal, but the thickness must satisfy certain conditions for transmission of the incident acoustic waves. When the housing 21 is metallic, its wall thickness will be between a few tenths of a millimeter and a few millimeters. The housing 21 imposes on the face .24 of the foam 20 a precise shape which must not change under the action of hydrostatic pressure. The external face 29 of the reflection device opposite to the external face 27 of the wall 21 is covered by a flexible envelope 30, for example made of elastomeric material a few millimeters thick. This closure member completes the sealing of the device while transmitting efficiently via the foam 20, the hydrostatic pressure that "is thus also applied on both sides of the rigid housing wall 21. As the rigidity of the flexible element closing does not prevent the external pressure from acting also inside, the stiffness provided by the housing 21 is sufficient to prevent any deformation resulting from the action of the hydrostatic pressure. The casing 30 can overflow so as to cover the rim (28) of the housing 21 to which it is fixed by means of an adhesive 23, contributing to the sealing of the assembly Advantageously, the casing 30 can cover the entire reflecting device of the flexible closing element which undergoes all the deformations which result from the crushing of the foam by hydrostatic pressure, but the presence of gaseous cells prevents packing which would undesirably modify the acoustic impedance used for r effectively deflecting incident acoustic waves.

La face 29 du réflecteur selon l'invention est munie de plots 25, par exemple en matière élastomère, situés sur les bords. Ces plots forment entretoise et permettent une bonne fixation sur le support 26. Ils permettent ainsi à la pression hydrostatique de s'exercer sur la face 29 du réflecteur.The face 29 of the reflector according to the invention is provided with studs 25, for example made of elastomeric material, situated on the edges. These studs form a spacer and allow good fixing on the support 26. They thus allow the hydrostatic pressure to be exerted on the face 29 of the reflector.

La mousse 20 réfléchit les ondes acoustiques. Pour obtenir une forte réflexion, on a vu que les conditions sont Z1 » Z2 avec Z1 = p l cl et Z2 =

Figure imgb0002
, où Y est le module d'Young, d l'épaisseur de la mousse, et ω la pulsation de l'onde acoustique incidente.The foam 20 reflects the acoustic waves. To obtain a strong reflection, we have seen that the conditions are Z 1 »Z 2 with Z 1 = p l c l and Z 2 =
Figure imgb0002
 , where Y is the Young's modulus, d the thickness of the foam, and ω the pulsation of the incident acoustic wave.

Il faut que Y ne varie pas notablement avec la pression hydrostatique, ce qui est réalisé convenablement avec les mousses viscoélastiques à alvéoles gazeuses.It is necessary that Y does not vary appreciably with the hydrostatic pressure, which is done properly with viscoelastic foams with gas cells.

La figure 2 illustre le comportement d'un dispositif réflecteur mou dont le milieu intérieur serait enfermé dans une enveloppe complètement rigide 101. La déformation sous l'action de la pression hydrostatique extérieure des deux éléments rigides 27 et 29 donne lieu aux déformées 270 et 290 représentées en pointillé en exagérant la déformation. Les éléments de paroi 28 peuvent aussi se déformer. Sur la figure 2, on a représenté un hydrophone 100 recevant des ondes acoustiques notamment de l'ensemble réflecteur 101. La déformation de la face 270 est à l'origine de différence de marche telles que l'écart A illustré sur la figure 2 modifie la phase de l'onde réfléchie. De plus, la courbure de la structure change du fait de la déformation, ce qui peut influencer la trajectoire des ondes acoustiques réfléchies. Les déformations indésirables du dispositif de la figure 2 résultent des différences de pressions hydrostatiques externes et internes.FIG. 2 illustrates the behavior of a soft reflector device, the internal environment of which would be enclosed in a completely rigid envelope 101. The deformation under the action of the external hydrostatic pressure of the two rigid elements 27 and 29 gives rise to the deformed parts 270 and 290 shown in dotted lines by exaggerating the deformation. The wall elements 28 can also deform. In FIG. 2, a hydrophone 100 is shown which receives acoustic waves in particular from the reflector assembly 101. The deformation of the face 270 is the cause of the path difference such that the difference A illustrated in FIG. 2 modifies the phase of the reflected wave. In addition, the curvature of the structure changes due to the deformation, which can influence the trajectory of the reflected acoustic waves. The undesirable deformations of the device of FIG. 2 result from the differences in external and internal hydrostatic pressures.

La figure 3 représente le dispositif de la figure 1 soumis à pression hydrostatique externe.Figure 3 shows the device of Figure 1 subjected to external hydrostatic pressure.

La pression hydrostatique, symbolisée par les flèches 32 s'exerce notamment sur les faces 27 et 29 du réflecteur. L'enveloppe 30 transmet intégralement la pression à la mousse viscoélastique 20, qui la transmet intégralement au boîtier rigide 21. Les pressions qui s'exercent sur ses deux faces principales étant les mêmes, le boîtier ne se déforme pas quand la pression hydrostatique varie. Pour résister à la pression hydrostatique, la mousse 20 d'épaisseur d, s'écrase. L'épaisseur d e est choisie de façon à ce que

Figure imgb0003
soit faible par rapport à ρ1 c1, à la fréquence la plus basse que l'on veut réfléchir avec le réflecteur. Il est à noter que Ci est l'épaisseur réduite de la mousse 20 à la profondeur maximale à laquelle le dispostif selon l'invention est destiné, de sorte qu'il faut choisir l'épaisseur d en conséquence.The hydrostatic pressure, symbolized by the arrows 32 is exerted in particular on the faces 27 and 29 of the reflector. The casing 30 fully transmits the pressure to the viscoelastic foam 20, which transmits it entirely to the rigid casing 21. The pressures exerted on its two main faces being the same, the casing does not deform when the hydrostatic pressure varies. To resist the hydrostatic pressure, the foam 20 of thickness d, is crushed. The thickness d e is chosen so that
Figure imgb0003
 is weak compared to ρ 1 c 1 , at the lowest frequency that we want to reflect with the reflector. It should be noted that Ci is the reduced thickness of the foam 20 at the maximum depth for which the device according to the invention is intended, so that the thickness d must be chosen accordingly.

La figure 4 illustre une variante de réalisation du dispositif selon l'invention où la paroi rigide 21 est une simple plaque fixée directement à la structure 26 au moyen d'un support formant cadre de montage 110. Des ouvertures 112 sont prévues dans le cadre 110, afin que la pression hydrostatique extérieure puisse agir sur la face 29 du dispositif. La face 29 appartient à un élément souple de fermeture qui enveloppe la mousse 20 et qui est collé de façon étanche contre la paroi 21.FIG. 4 illustrates an alternative embodiment of the device according to the invention where the rigid wall 21 is a simple plate fixed directly to the structure 26 by means of a support forming a mounting frame 110. Openings 112 are provided in the frame 110 , so that the external hydrostatic pressure can act on the face 29 of the device. The face 29 belongs to a flexible closing element which envelops the foam 20 and which is sealed against the wall 21.

L'invention n'est pas limitée au cas d'un dispositif à réflexion d'onde entièrement passif. Dans certains cas, un dispositif réflecteur mou peut être muni par exemple d'un feuillet de matériau piézoélectrique 31 placé entre électrodes pour réaliser la fonction transducteur à l'émission ou à la réception. Cette variante est illustrée sur la figure 5.The invention is not limited to the case of a fully passive wave reflection device. In some cases, a soft reflector device can be provided, for example, with a sheet of piezoelectric material 31 placed between electrodes to perform the transducer function on transmission or on reception. This variant is illustrated in FIG. 5.

Les dispositifs réflecteurs précédemment décrits sont particulièrement bien adaptés à la réalisation d'antennes d'écoute passive qui comportent un ou plusieurs hydrophones. Dans une antenne de ce type, les hydrophones sont situés en face d'une surface réflectrice composée d'un ensemble de dispositifs tels que décrits précédemment. La plus courte distance séparant chaque hydrophone de la surface réflectrice est avantageusement égale à λ/4 où À est la longueur d'onde correspondant à la fréquence centrale de la bande d'écoute des hydrophones.The reflector devices described above are particularly well suited to the production of passive listening antennas which include one or more hydrophones. In an antenna of this type, the hydrophones are located opposite a reflecting surface composed of a set of devices as described above. The shortest distance separating each hydrophone from the reflecting surface is advantageously equal to λ / 4 where λ is the wavelength corresponding to the central frequency of the listening band of the hydrophones.

La figure 6 illustre un exemple de disposition des réflecteurs 41 et d'hydrophones 40, dans une antenne d'écoute passive utilisant une surface réflectrice de forme cylindrique. Dans l'exemple de la figure 6, les réflecteurs 41 ont une surface réflectrice élémentaire de forme carrée et les hydrophones 40 sont situés à l'aplomb du centre de symétrie de chaque surface élémentaire. Les réflecteurs 41 sont maintenus jointivement sur une embase au moyen d'étriers 42 maintenus par des tirants 43, par exemple en acier.FIG. 6 illustrates an example of arrangement of the reflectors 41 and hydrophones 40, in a passive listening antenna using a reflective surface of cylindrical shape. In the example of FIG. 6, the reflectors 41 have an elementary reflective surface of square shape and the hydrophones 40 are located directly above the center of symmetry of each elementary surface. The reflectors 41 are held contiguously on a base by means of stirrups 42 held by tie rods 43, for example of steel.

La figure 7 est une vue en coupe du dispositif de la figure 6. L'embase 26 de l'antenne étant par exemple cylindrique, les réflecteurs 41 sont courbés pour épouser la structure et sont maintenus jointivement au moyen d'étriers 42 retenus par des tirants d'acier 43 sur l'embase 26. Des trous 45 permettent à l'eau d'exercer la pression hydrostatique sur les faces 29 des dispositifs réflecteurs selon l'invention.Figure 7 is a sectional view of the device of Figure 6. The base 26 of the antenna being for example cylindrical, the reflectors 41 are curved to match the structure and are held contiguously by means of stirrups 42 retained by steel tie rods 43 on the base 26. Holes 45 allow the water to exert hydrostatic pressure on the faces 29 of the reflector devices according to the invention.

La figure 8 illustre un exemple de disposition analogue à celui de la figure 6, mais où les réflecteurs 41 sont triangulaires. Il est évident que d'autres dispositions de réflecteurs et d'hydrophones peuvent être adoptées sans sortir du cadre de la présente invention.FIG. 8 illustrates an example of an arrangement similar to that of FIG. 6, but where the reflectors 41 are triangular. It is obvious that other arrangements of reflectors and hydrophones can be adopted without departing from the scope of the present invention.

Claims (11)

1. Dispositif à réflexion d'ondes acoustiques selon une interface (24) séparant un volume de matériau (20) viscoélastique à alvéoles gazeuses d'un matériau (21) perméable auxdites ondes acoustiques qui sert à isoler ce volume du milieu fluide extérieur à densité supérieure, caractérisé en ce que ledit volume (20) est appliqué contre une paroi rigide (21) faite dudit matériau perméable ; ladite paroi étant portée par un support rigide (26), un élément souple de fermeture (30) coopérant avec ladite paroi rigide pour assurer l'étanchéité dudit dispositif tout en transmettant audit volume la pression hydrostatique extérieure, afin d'empêcher la déformation et le changement de position de l'interface (24) dont la forme est imposée par ladite paroi rigide (21).1. Device for reflecting acoustic waves according to an interface (24) separating a volume of viscoelastic material (20) with gaseous cells from a material (21) permeable to said acoustic waves which serves to isolate this volume from the external fluid medium at density upper, characterized in that said volume (20) is applied against a rigid wall (21) made of said permeable material; said wall being carried by a rigid support (26), a flexible closing element (30) cooperating with said rigid wall to ensure the tightness of said device while transmitting to said volume the external hydrostatic pressure, in order to prevent deformation and change of position of the interface (24) whose shape is imposed by said rigid wall (21). 2. Dispositif selon la revendication 1, caractérisé par le fait que ladite paroi (21) comporte un rebord (28) de façon à former un boîtier ouvert.2. Device according to claim 1, characterized in that said wall (21) has a flange (28) so as to form an open housing. 3. Dispositif selon l'une quelconque des revendications 1 ou 2, caractérisé par le fait que le matériau viscoélastique déformable (20) est une mousse viscoélastique en caoutchouc, chlorure de polyvinyle, polyéthylène ou acétate d'éthylène et de vinyle (EVA).3. Device according to any one of claims 1 or 2, characterized in that the deformable viscoelastic material (20) is a viscoelastic foam of rubber, polyvinyl chloride, polyethylene or ethylene and vinyl acetate (EVA). 4. Dispositif selon l'une quelconque des revendications 1 à 3, caractérisé par le fait que l'élément souple de fermeture (30) est une membrane de matériau élastomère.4. Device according to any one of claims 1 to 3, characterized in that the flexible closure element (30) is a membrane of elastomeric material. 5. Dispositif selon l'une quelconque des revendications 1 à 4, caractérisé par le fait que l'élément de fermeture (30) entoure complètement ledit dispositif.5. Device according to any one of claims 1 to 4, characterized in that the closure element (30) completely surrounds said device. 6. Dispositif selon l'une quelconque des revendications 1 à 5, caractérisé par le fait que la paroi rigide (21) est réalisée en métal.6. Device according to any one of claims 1 to 5, characterized in that the rigid wall (21) is made of metal. 7. Dispositif selon l'une quelconque des revendications 1 à 5, caractérisé par le fait que la paroi rigide (21) est faite d'un matériau organique de synthèse.7. Device according to any one of claims 1 to 5, characterized in that the rigid wall (21) is made of an organic synthetic material. 8. Dispositif selon l'une quelconque des revendications 1 à 7, caractérisé par le fait que la face externe (29) de l'élément de fermeture (30) est reliée au support (26) par des entretoises (25) laissant accéder l'eau de mer à cette face externe (29).8. Device according to any one of claims 1 to 7, characterized in that the external face (29) of the closure element (30) is connected to the support (26) by spacers (25) allowing access to the sea water to this external face (29). 9. Dispositif selon l'une quelconque des revendications 1 à 8, caractérisé en ce que à la plus basse fréquence des ondes acoustiques à réfléchir, l'impédance acoustique par unité de surface du fluide est supérieure à l'impédance acoustique manifestée par le volume de mousse viscoélastique à alvéoles gazeuses.9. Device according to any one of claims 1 to 8, characterized in that at the lowest frequency of the acoustic waves to be reflected, the acoustic impedance per unit area of the fluid is greater than the acoustic impedance manifested by the volume viscoelastic foam with gas cells. 10. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comporte un élément transducteur piézoélectrique (31) contigü à la paroi rigide (21).10. Device according to any one of the preceding claims, characterized in that it comprises a piezoelectric transducer element (31) contiguous to the rigid wall (21). 11. Antenne d'écoute passive caractérisée en ce qu'elle comporte au moins un dispositif selon l'une quelconque des revendications précédentes.11. Passive listening antenna characterized in that it comprises at least one device according to any one of the preceding claims.
EP19840400076 1983-01-19 1984-01-13 Interface device for acoustic wave reflection Expired EP0114764B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8300753A FR2539541B1 (en) 1983-01-19 1983-01-19 DEVICE WITH ACOUSTIC WAVE REFLECTIVE INTERFACE
FR8300753 1983-01-19

Publications (3)

Publication Number Publication Date
EP0114764A2 true EP0114764A2 (en) 1984-08-01
EP0114764A3 EP0114764A3 (en) 1984-08-22
EP0114764B1 EP0114764B1 (en) 1987-09-02

Family

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Application Number Title Priority Date Filing Date
EP19840400076 Expired EP0114764B1 (en) 1983-01-19 1984-01-13 Interface device for acoustic wave reflection

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EP (1) EP0114764B1 (en)
AU (1) AU2355484A (en)
CA (1) CA1239693A (en)
DE (1) DE3465809D1 (en)
ES (1) ES8503449A1 (en)
FR (1) FR2539541B1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2204217A (en) * 1987-05-02 1988-11-02 Gec Avionics Acoustic reflector
EP0435753A1 (en) * 1989-12-29 1991-07-03 Thomson-Csf Acoustic wave reflector for functioning at great depths of immersion
EP0328931A3 (en) * 1988-02-18 1991-07-31 The B.F. Goodrich Company Compliant tube baffle
EP0506529A1 (en) * 1991-03-29 1992-09-30 Thomson-Csf Directional antenna for low frequency acoustic waves
FR2720590A1 (en) * 1994-05-31 1995-12-01 Thomson Csf Absorbent passive acoustic antenna.

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115482805B (en) * 2022-08-03 2025-10-31 中国船舶重工集团公司第七一九研究所 Acoustic super-surface capable of regulating and controlling underwater sound wave reflection sound field

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2811216A (en) * 1954-04-28 1957-10-29 Harris Transducer Corp Acoustic baffle construction
US2884084A (en) * 1954-10-28 1959-04-28 Sussman Harry Acoustic panel
DE1815684A1 (en) * 1968-12-19 1970-06-25 Krupp Gmbh Reflector for water-borne noise
FR2240813B1 (en) * 1973-08-16 1976-04-30 France Etat

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2204217A (en) * 1987-05-02 1988-11-02 Gec Avionics Acoustic reflector
GB2204217B (en) * 1987-05-02 1990-05-23 Gec Avionics Acoustic reflector
EP0328931A3 (en) * 1988-02-18 1991-07-31 The B.F. Goodrich Company Compliant tube baffle
EP0435753A1 (en) * 1989-12-29 1991-07-03 Thomson-Csf Acoustic wave reflector for functioning at great depths of immersion
FR2656720A1 (en) * 1989-12-29 1991-07-05 Thomson Csf ACOUSTIC WAVE REFLECTOR THAT CAN OPERATE UNDER STRONG IMMERSION.
US5099457A (en) * 1989-12-29 1992-03-24 Thomson-Csf Acoustic wave reflector capable of working under deep submersion
EP0506529A1 (en) * 1991-03-29 1992-09-30 Thomson-Csf Directional antenna for low frequency acoustic waves
FR2674717A1 (en) * 1991-03-29 1992-10-02 Thomson Csf LOW FREQUENCY DIRECTIVE ACOUSTIC ANTENNA.
FR2720590A1 (en) * 1994-05-31 1995-12-01 Thomson Csf Absorbent passive acoustic antenna.
US5600609A (en) * 1994-05-31 1997-02-04 Thomson-Csf Absorbent passive acoustic antenna

Also Published As

Publication number Publication date
FR2539541A1 (en) 1984-07-20
ES528948A0 (en) 1985-02-16
AU2355484A (en) 1984-07-26
DE3465809D1 (en) 1987-10-08
EP0114764B1 (en) 1987-09-02
ES8503449A1 (en) 1985-02-16
EP0114764A3 (en) 1984-08-22
FR2539541B1 (en) 1986-09-19
CA1239693A (en) 1988-07-26

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