WO2011021018A1 - Réflecteur acoustique - Google Patents

Réflecteur acoustique Download PDF

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Publication number
WO2011021018A1
WO2011021018A1 PCT/GB2010/051163 GB2010051163W WO2011021018A1 WO 2011021018 A1 WO2011021018 A1 WO 2011021018A1 GB 2010051163 W GB2010051163 W GB 2010051163W WO 2011021018 A1 WO2011021018 A1 WO 2011021018A1
Authority
WO
WIPO (PCT)
Prior art keywords
acoustic
reflector
reflectors
acoustic reflector
corner
Prior art date
Application number
PCT/GB2010/051163
Other languages
English (en)
Inventor
Carl Tiltman
Andrew Malcolm Tulloch
Carl Duncan Holmes
Original Assignee
Subsea Asset Location Technology Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from GB0914455A external-priority patent/GB0914455D0/en
Priority claimed from GB0914462A external-priority patent/GB0914462D0/en
Priority claimed from GBGB1001804.2A external-priority patent/GB201001804D0/en
Application filed by Subsea Asset Location Technology Limited filed Critical Subsea Asset Location Technology Limited
Priority to AU2010284850A priority Critical patent/AU2010284850A1/en
Priority to EP10735328A priority patent/EP2467848A1/fr
Priority to GB1202036.8A priority patent/GB2485698A/en
Publication of WO2011021018A1 publication Critical patent/WO2011021018A1/fr

Links

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
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/20—Reflecting arrangements
    • G10K11/205—Reflecting arrangements for underwater use
    • 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
    • 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
    • G10K11/26—Sound-focusing or directing, e.g. scanning
    • G10K11/28—Sound-focusing or directing, e.g. scanning using reflection, e.g. parabolic reflectors
    • 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
    • G10K2200/00—Details of methods or devices for transmitting, conducting or directing sound in general
    • G10K2200/11—Underwater, e.g. transducers for generating acoustic waves underwater

Definitions

  • This invention relates to acoustic reflectors. There is a demand for a simple to make, very cheap reflector for use in less demanding situations. Previous attempts. For example,
  • Patent Citation 0001 US 3195677 B (HILLARY ET AL). 1965-07-20.
  • Patent Citation 0002 US 4303144 B (WIRT). 1981-12-01.
  • Patent Citation 0003 WO WO 2006/075167 A (THE SECRETARY OF STATE FOR DEFENCE). 2006-07-20.
  • Patent Citation 0004 WO WO 2009/122184 A (THE SECRETARY OF STATE FOR DEFENCE). 2009-10-08.
  • an acoustic reflector comprises at least one
  • elongate member having one or a plurality of acoustic reflecting elements disposed around its axis.
  • an elongate member means a member whose length along a central axis is greater than a cross section measured orthogonally to the axis.
  • an acoustic reflector as aforesaid comprises at least two such members mounted substantially orthogonally to each other.
  • the acoustic reflecting elements may comprise elongate corner reflectors substantially parallel to the axis of the member(s).
  • the acoustic reflecting elements may comprise elongate parabolic reflectors substantially parallel to the axis of the member.
  • the acoustic reflecting elements comprise elongate partially elliptical reflectors substantially parallel to the axis of the member.
  • the acoustic reflecting elements are different on at least two different members.
  • one or more of the members may have one or more annular pieces disposed around them, to present surfaces orthogonal to the surface of the members.
  • the elongate members are substantially cylindrical with acoustic reflecting elements formed on the outer surface of the cylinder parallel to the axis.
  • the elongate members are arranged in a T configuration.
  • the reflector comprises parallel elongate members joined by a cross member.
  • individual acoustic reflecting elements are formed in the surface of the elongate members. These individual reflecting elements may be corner reflectors, parabolic reflectors or partial elliptical reflectors.
  • an acoustic reflector has an elongate member comprising a plurality of pairs of individual reflecting elements the pairs being disposed in back to back pairs around the axis of the elongate member.
  • the pairs may be arranged to be rotated with respect to one another around the axis such that the angle of rotation of one pair with respect to an adjoining pair is ⁇ /xn where n is the number of pairs along the length of the member and x is a whole number, normally x is 1.
  • a corner reflector is provided at each end of the stack wherein the corner of the reflector is perpendicular to the longitudinal axis of the stack.
  • the members are made from polyurethane which may be extruded or moulded in the elongate shape required. If the reflector comprises a plurality of members to be made from extruded polyurethane or the like, they can be cut to the required lengths and lengths fixed together in the required arrangement by friction or hot air welding. To improve acoustic reflecting characteristics the reflecting elements can be lined with a good acoustic reflecting material such as aluminium.
  • the acoustic reflector comprises pairs of individual reflecting elements as described in paragraphs [0014 and 0015]
  • the reflectors can be fabricated separately or in pairs and mounted on a central rod.
  • glass reinforced plastics may be used for the members as can metals such as aluminium.
  • metals such as aluminium.
  • metals such as aluminium may be particularly useful for cheaply fabricating the acoustic reflector described in paragraph [0015] and subsequent injection moulded elements may be cheaply formed from glass filled polymers and welded together to form a monolithic reflector.
  • a system to disguise or protect an underwater object comprises a plurality of acoustic reflectors according to this invention.
  • Systems of this kind can be used for protecting vessels against threats, say from a target seeking torpedo, which identifies potential targets by sonar sounding, or for rendering the vessel invisible to the sonar of submarines or ships or to so called dunking sonar systems.
  • the system can also be used to mask the emitted acoustic signal of a vessel by scattering the emitted sound and allowing a vessel to leave port, for example, without being detected by acoustic listening devices.
  • buoyancy may be an issue, with the reflectors tending to sink or rise to the surface of the water. If this is the case the reflectors could be weighted to provide neutral buoyancy at normal deployment depths.
  • the cheapness of reflectors described in this invention enables large numbers to be deployed, and if not recovered the economic loss would be low.
  • figure 1 shows an acoustic reflector according to the invention in a T-configuration
  • figure 2 shows the acoustic reflector figure 1 sectioned on the line A-A' of figure 1;
  • figure 3 shows an acoustic reflector according to the invention in an I shape configuration
  • figure 4 shows the reflector of figure 3 sectioned on the line B-B' of figure 3;
  • figure 5 shows an acoustic reflector according to the invention in which individual reflectors are formed in the surface of the members;
  • figure 6 shows a section on the line C-C of figure 5.
  • figure 7 shows a perspective view of a simple reflector according to the invention
  • figure 8 shows a further embodiment of the invention sectioned on the line A-A' figure 9;
  • Figure 9 is a side view of the further embodiment
  • Figure 10 shows an alternative arrangement of the further embodiment shown in figures 8 and 9;
  • Figure 11 shows a pipe section with elongate acoustic reflectors having a cross section as shown in figure 2;
  • Figure 12 shows the use of elongate acoustic reflectors according to the invention to identify scouring around an object, such as a bridge support, in water.
  • an acoustic reflector 10 comprises a pair of elongate orthogonal members 12 and 14 mounted in a T configuration.
  • the members 12 and 14 are substantially cylindrical with elongate corner reflectors 16 formed in the surfaces 18 of the cylinders, the reflectors are parallel to the axes 20 of the members 12 and 14.
  • the reflectors 16 can be seen in cross-section in figure 2.
  • the members 12 and 14 have been cut to length from an extruded length of polyurethane and friction welded together at their join 22.
  • Annular members 24 are disposed around the orthogonal members 12 and 14, tightly fitting into groves in the surface 18 of the members 14 and 16 formed by the elongate corner reflectors 16.
  • the annular members 24 are mouldings with their inner holes shaped to correspond with the grooves formed by the corner reflectors 16.
  • the annular members are glued in place.
  • the shape of the annular members 24, is such as to provide two surfaces that are orthogonal to the axis of members 12 and 14, to form a pair of right angles with respect to the surfaces of reflectors 16.
  • a reflector 30 according to the invention comprises parallel
  • members 32 and 33 bridged at their mid-points by member 34, which is orthogonal to each of members 32 and 33,.
  • the members 32, 33 and 34 are substantially cylindrical with elongate parabolic reflectors 36 formed in the surfaces 38 of the cylinders parallel to their axes 40.
  • the parabolic reflectors 36 can be seen in cross-section in figure 4.
  • the members 32, 33 and 34 had been cut to length from an excluded length of polyurethane and friction welded together at their joints 42 and 43.
  • Annular members 44 are disposed around the orthogonal members 32, 33 and 34 tightly fitting into groves in the surface 38 of the members 32, 33 and 34 formed by the elongate parabolic reflectors 36.
  • the annular members 44 are mouldings with their inner holes shaped to correspond with the grooves formed by the parabolic reflectors 36.
  • the annular members are glued in place.
  • the shape of the annular members 44 is such as to provide two surfaces that are orthogonal to the axis of members 32, 33 and 34, to form a pair of right angles with respect to the surfaces of reflectors 36.
  • the orthogonal members 12, 14, 32, 33 and 34 will typically be around 200mm in diameter. These members can be as long as required, ranging up to several metres.
  • the annular members 24 and 44 would be disposed along the length of members 12, 14, 32, 33, and 34 at least one every metre, but their separation can be much less than this, say, every 200mm.
  • An individual reflector is shown by the cross section shown in figure 6, where it is seen as a corner reflector having a right angle 58 between two adjacent faces 59 and 60 of the reflector.
  • an incoming acoustic wave 64 striking one face 59 will be reflected to the other face 60, which in turn reflects the wave back.
  • the final reflected wave 66 travels in the opposite direction to the incoming wave 64 and can be detected conventionally.
  • Parabolic and partial elliptic reflectors work in the same way by initially reflecting an incoming acoustic wave internally from one surface to another, the second surface then reflects the wave out of the reflector in the opposite direction to the incoming wave.
  • the combination of reflectors 16 or 36, with annular members 24 or 44 respectively behaves in the same way as the individual corner reflectors of figures 5 and 6, but is easier to make in large sizes.
  • T and I acoustic reflectors have been described, in practice the orthogonal members can be assembled in many ways, as a X, E, FI, H etc..
  • FIG. 7 shows a very simple device according to the invention.
  • an acoustic reflector 70 comprises a pair of rectangular crossed planks 72 and 74 (the planks may be continuous, and joined by conventional carpentry joints, or the planks may be in parts and simply glued or welded together at the crossing points. However assembled, the planks intersect orthogonally so that four corner acoustic reflectors 76 are created in each of the four right angles formed by the crossing point.
  • the planks may have annular members similar to those shown as 24 and 44, but with a rectangular central hole, disposed as a tight fit around their surface, the annular member is shaped in such a way that it has two surfaces that form rights angles with the surface of the plank.
  • a backing sheet can be attached to the X formed by the planks such that the right angles are also formed between the planks and the backing sheet.
  • the planks may have a partially parabolic surface, if this provides the reflecting characteristics needed.
  • an acoustic reflector element 110 part of an elongate member comprising an acoustic reflector according to the invention, comprises a pair of corner reflectors 11OA and HOB arranged back to back.
  • Each reflector 11OA and HOB comprises a pair of reflective surfaces 112, 114, arranged perpendicularly to each other, with reflective top and bottom surfaces 116 of the reflector element 110 orthogonally mounted with respect to both surfaces 112 and 114.
  • each reflector 11OA and HOB are positioned back to back along a common axis 118.
  • element 110 is located above two substantially identical elements 120 and 130 as shown in figure 2. Each element 20, 30 is rotated by ⁇ /3 (60°) from element 110 and from each other so that the entire device gives six responses equally spaced at 60° intervals viewed azimuthally. Lugs 105 are inserted into location holes 103 to secure the elements together in their desired relative positions.
  • the outside of the acoustic reflector device 101 is generally of cylindrical shape. The device 101 is supported by a rod 107 which may be arranged to extend through a hole along the central axis of the device.
  • the acoustic reflector 101 is manufactured by preparing three cylinders of a foamed plastics material such as polyurethane each corresponding to the shape of a reflector element 110, 120, 130.
  • the material is one that will not itself reflect acoustic waves at the frequencies of interest.
  • the material is then cut along the surfaces defining the reflector surfaces 112, 114 and the top and bottom plates 16.
  • Each of the surfaces is lined with a material that will reflect acoustic waves at the frequency of interest. This may be aluminium, for example.
  • the three corner reflecting pairs 110, 120, 130 prepared in this way are to each other by means of holes 103 and lugs 105 in the top and bottom plates 116, rod 107 passes through the longitudinal axis of the device 101 in combination with lugs and holes 103 and 105 maintains the individual elements 110, 120, 130 in place element si 10, 120, 130 may be glued together.
  • the ends of the stack may be finished with further reflectors, reflecting acoustic signals in the parallel to the longitudinal axis of the stack.
  • the reflector 170 is collapsible. It comprises a stack of three pairs 182, 184, 186 of corner reflectors. Each corner reflector comprises aluminium reflector plates 172 and 174, and hinged along axis 176, orthogonal to the longitudinal axis 90 - 90' of the element. The assembly may be spring-loaded into its erected disposition and each pair of aluminium plates 172 and 174, held in its position by a spacer 178, such that an internal angle of 90° is maintained between the reflector plates 172 and 174. Each member of each pair of corner reflectors is mounted back to back with their hinges 176 common.
  • the pairs 182, 184, 186 of reflectors are mounted in a stack with circular aluminium plates between them and the d the longitudinal axis 90-90' at their centres and perpendicular to their planes.
  • the inactive spaces 192 formed between the various plates when in position can be filled with acoustic absorbing foam to help maintain the plates 172 and 174 in position when the device is deployed.
  • the axis 176 of the of reflectors 184 is at ⁇ /3 (60°) to the axis 176 of the reflector pair 182; likewise the axis 176 of reflector pair 186 turned by a further ⁇ /3 (60°) to the axis 176 in respect of the reflector pair 182.
  • the edges of each plate 172 and 174 are cut such that in plan, looking in the direction 90 to 90' the whole device is circular.
  • the stack may comprise four reflector elements with adjacent elements being relatively rotated by substantially ⁇ /4 instead of ⁇ /3 as would be the case for the three element stack.
  • reflectors can be provided at each end additionally to reflect acoustic waves along the longitudinal axis of the device.
  • FIG 11 shows a schematic diagram of a pipe section 530 fitted with a number of acoustic reflectors 532 each according to the invention and comprising an elongate aluminium member having a cross section as shown in figure 2.
  • Each reflector comprises an aluminium rod 536, with elongate reflectors 534 formed in its surface (the detail of these can be seen in figure X).
  • Each of elongate cylindrical ends 538 of the reflectors 532 is capped and closed off by a conventional electrically insulating material, which, in particular isolates the aluminium rods from the pipe section 530 and prevents any electrical conduction there between.
  • the reflectors 532 are attached to the pipe section 530 by upstanding lugs 542 fitted to the pipes.
  • the acoustic reflectors 532 are electrically isolated from the pipe sections 530 with insulating bushes (not shown) fitted to the end of the lugs in a conventional manner. Aluminium members 540 fitted around the rods 536 may be provided in a similar manner to the annular members 24 mentioned in paragraph [0039].
  • the pipe section 530 has conventional end flanges 531 with holes therein allowing it to be bolted to another pipe section.
  • the pipe section with the acoustic reflectors can be prefabricated on land and joined by means of the bolt holes in the flanges 531 to another like fitted pipe. In this way, a pipe line fitted with acoustic reflectors can be assembled as part of the normal process for laying an underwater pipeline.
  • the invention thus provides a neat and economical way of ensuring that underwater pipelines can be identified.
  • plastic extrusions may be used for the reflectors with annular members fitted in the same way. If such materials are used insulation of the lugs and rod ends is avoided. Performance will not be as good as the aluminium extrusion, but if the reflectors 536 are lined with aluminium and aluminium annular members 540 provided the performance will be similar to the wholly aluminium reflector. Although aluminium has been described because of its lightness and ease of extrusion, other metals and acoustic reflecting materials can be used instead.
  • the elongate reflector in figure 11 has been described in relation to a pipe section, the reflectors can be applied to other underwater objects, such as oil rig platforms, accommodation platforms for workers at sea, and other objects to be placed under water.
  • FIG. 12 An example of one of these alternative applications is shown in figure 12.
  • the lower portion of a bridge pier 660 is shown extending below surface of the sea bed 666.
  • the progressive effects of scouring of the sea bed are shown by lines 667 and 668.
  • the pier 660 (although it could be a drilling platform, stanchion or the like) extends below the sea surface 665, is mounted in the sea bed 666.
  • a series of acoustic reflectors 661, 662, 663 and 664 is mounted on the pier.
  • the reflectors are elongate aluminium rods having a cross section as shown in figure 2 with orthogonal aluminium annuli mounted thereon as described in paragraph [0039].
  • the series of rods may be formed around the pier, or a single rod bend all the way round in effect as shown in figure 12.
  • Reflectors 661 and 662 are permanently above the sea bed and can be used to mark the pier 660. Currents will scour the sea bed preferentially around the pier 660, eventually lowering the sea bed level to 667 exposing reflector 663 which was initially below the sea bed. Identification of this reflector 663 by interrogation by a sonar signal will provide an early warning of scouring, and the need for possible attention. As scouring continues and the sea bed drops further as indicated by line 668, a second reflector 664 is exposed, which may indicate that a potentially dangerous situation has developed and the underwater mounting of support item 660 may need urgent attention.
  • rods reflectors Although four acoustic reflectors have been illustrated in figure 12, more or less may be used to suit the relevant design criteria. Although aluminium reflectors have been described the rods can be made from any suitable material. As an alternative to rods reflectors of the configurations shown in figures 1 to 4 could be used.

Landscapes

  • 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

La présente invention concerne un réflecteur acoustique (10) comprenant au moins un élément allongé (12, 14) doté d'une pluralité de moyens réflecteurs (16) disposés autour de son axe. La présente invention concerne divers modes de réalisation. Dans l'un d'eux, deux de ces éléments (12, 14) sont montés de façon sensiblement orthogonale l'un par rapport à l'autre. Dans un autre mode de réalisation, les réflecteurs sont agencés par paires opposées autour d'un axe, les paires adjacentes étant mises en rotation par rapport à la paire suivante pour permettre à chacune des ondes acoustiques entrantes provenant de diverses directions d'être réfléchies.
PCT/GB2010/051163 2009-08-19 2010-07-16 Réflecteur acoustique WO2011021018A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AU2010284850A AU2010284850A1 (en) 2009-08-19 2010-07-16 Acoustic reflector
EP10735328A EP2467848A1 (fr) 2009-08-19 2010-07-16 Réflecteur acoustique
GB1202036.8A GB2485698A (en) 2009-08-19 2010-07-16 Acoustic reflector

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB0914455.1 2009-08-19
GB0914462.7 2009-08-19
GB0914455A GB0914455D0 (en) 2009-08-19 2009-08-19 Acoustic reflector
GB0914462A GB0914462D0 (en) 2009-08-19 2009-08-19 Acoustic scattering devices
GB1001804.2 2010-02-04
GBGB1001804.2A GB201001804D0 (en) 2010-02-04 2010-02-04 Acoustic reflectors

Publications (1)

Publication Number Publication Date
WO2011021018A1 true WO2011021018A1 (fr) 2011-02-24

Family

ID=42813293

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2010/051163 WO2011021018A1 (fr) 2009-08-19 2010-07-16 Réflecteur acoustique

Country Status (4)

Country Link
EP (1) EP2467848A1 (fr)
AU (1) AU2010284850A1 (fr)
GB (1) GB2485698A (fr)
WO (1) WO2011021018A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
MX2013000444A (es) * 2010-07-16 2013-06-05 Subsea Asset Location Tech Ltd Reflectores acusticos.

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1121981A (en) 1914-02-28 1914-12-22 Domenico Costarella Lever-jack.
FR1241240A (fr) * 1959-08-05 1960-09-16 Enceinte acoustique rigide à circuits accordés multiples
US3195677A (en) 1962-02-28 1965-07-20 Herbert V Hillery Triplane reflector with controlled frequency-dependent target strength
US4126847A (en) * 1975-07-15 1978-11-21 Westinghouse Electric Corp. Passive acoustic navigation aid
US4303144A (en) 1979-12-21 1981-12-01 Lockheed Corporation Apparatus for the retroreflection of sound
DE4323212A1 (de) * 1993-07-12 1995-01-19 Honeywell Elac Nautik Gmbh Vorrichtung zum Behandeln strömender Medien mit Ultraschall
US6209680B1 (en) * 2000-04-10 2001-04-03 Jay Perdue Acoustic diffuser panels and wall assembly comprised thereof
WO2005025767A1 (fr) * 2003-09-11 2005-03-24 Fsi International, Inc. Diffuseurs acoustique pour uniformite de champ acoustique
WO2006075167A1 (fr) 2005-01-14 2006-07-20 The Secretary Of State For Defence Reflecteur acoustique
US20070001965A1 (en) 2005-06-30 2007-01-04 Lg.Philips Lcd Co., Ltd. Driving integrated circuit of liquid crystal display device and driving method thereof
US20080164094A1 (en) * 2005-04-14 2008-07-10 Magyari Douglas P Acoustic Scatterer
WO2009122184A2 (fr) 2008-04-02 2009-10-08 The Secretary Of State For Defence Réflecteur acoustique accordable

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1121981A (en) 1914-02-28 1914-12-22 Domenico Costarella Lever-jack.
FR1241240A (fr) * 1959-08-05 1960-09-16 Enceinte acoustique rigide à circuits accordés multiples
US3195677A (en) 1962-02-28 1965-07-20 Herbert V Hillery Triplane reflector with controlled frequency-dependent target strength
US4126847A (en) * 1975-07-15 1978-11-21 Westinghouse Electric Corp. Passive acoustic navigation aid
US4303144A (en) 1979-12-21 1981-12-01 Lockheed Corporation Apparatus for the retroreflection of sound
DE4323212A1 (de) * 1993-07-12 1995-01-19 Honeywell Elac Nautik Gmbh Vorrichtung zum Behandeln strömender Medien mit Ultraschall
US6209680B1 (en) * 2000-04-10 2001-04-03 Jay Perdue Acoustic diffuser panels and wall assembly comprised thereof
WO2005025767A1 (fr) * 2003-09-11 2005-03-24 Fsi International, Inc. Diffuseurs acoustique pour uniformite de champ acoustique
WO2006075167A1 (fr) 2005-01-14 2006-07-20 The Secretary Of State For Defence Reflecteur acoustique
US20080164094A1 (en) * 2005-04-14 2008-07-10 Magyari Douglas P Acoustic Scatterer
US20070001965A1 (en) 2005-06-30 2007-01-04 Lg.Philips Lcd Co., Ltd. Driving integrated circuit of liquid crystal display device and driving method thereof
WO2009122184A2 (fr) 2008-04-02 2009-10-08 The Secretary Of State For Defence Réflecteur acoustique accordable

Also Published As

Publication number Publication date
GB201202036D0 (en) 2012-03-21
AU2010284850A1 (en) 2012-03-01
EP2467848A1 (fr) 2012-06-27
GB2485698A (en) 2012-05-23

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