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WO2003032012A1 - Source sonore immergee - Google Patents

Source sonore immergee Download PDF

Info

Publication number
WO2003032012A1
WO2003032012A1 PCT/GB2002/004473 GB0204473W WO03032012A1 WO 2003032012 A1 WO2003032012 A1 WO 2003032012A1 GB 0204473 W GB0204473 W GB 0204473W WO 03032012 A1 WO03032012 A1 WO 03032012A1
Authority
WO
WIPO (PCT)
Prior art keywords
gas
liquid
liquid mixture
pipe assembly
pipe
Prior art date
Application number
PCT/GB2002/004473
Other languages
English (en)
Inventor
Peter Dobbins
Original Assignee
Bae Systems (Land And Sea Systems) 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
Application filed by Bae Systems (Land And Sea Systems) Limited filed Critical Bae Systems (Land And Sea Systems) Limited
Publication of WO2003032012A1 publication Critical patent/WO2003032012A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/02—Generating seismic energy
    • G01V1/133—Generating seismic energy using fluidic driving means, e.g. highly pressurised fluids; using implosion
    • 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
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/04—Sound-producing devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/30—Assessment of water resources

Definitions

  • the present invention relates to underwater sound sources and is more particularly, although not exclusively, concerned with the generation of sound waves in a liquid, for example, seawater.
  • a continuous sound source for example, in applications such as sonar and signalling
  • a number of different techniques have been utilised.
  • Large transducers and other electrically powered sound sources have been used in systems using such techniques, and the power requirements for ship- and submarine-borne systems are not insignificant.
  • Methods for producing continuous sound underwater have been an area of significant research.
  • DE20008371 discloses a mouth organ arrangement which can be plunged into water.
  • the arrangement includes a musical vibrating air column pipe which has an extension piece enabling a brief tone to sound when the end of the air column pipe is plunged into water.
  • the arrangement produces the brief tone when the pipe is plunged into water so that the water drives air through the pipe to produce the tone.
  • US3924560 discloses a birdcall whistle which has water filled chambers.
  • seawater for example, seawater
  • JP7203579 discloses such an arrangement.
  • An air bubble-mixing device is connected to both a gas supply and a water supply to form and discharge a water/bubbles mixture in the vicinity of the signal sound wave which is generated by a separate transmitter.
  • GB2322506 discloses an underwater acoustic arrangement in which a low frequency sound wave is generated.
  • the arrangement comprises a low frequency underwater sound source and a bubble generator.
  • the bubble generator forms pressurised gas bubbles in a plume from an outlet of the generator.
  • the sound source applies a varying pressure to the plume of bubbles to modulate the plume and to generate the low frequency sound wave.
  • JP7203579 discloses the use of bubbles to modulate a sound source
  • GB2322506 discloses the use of bubbles as a resonator, neither document discloses using a bubbly liquid as the driving medium of a sound generator.
  • sound generating apparatus which utilises a gas/liquid mixture to modify the sounds speed or resonant frequency of a pipe assembly.
  • sound generating apparatus comprising a pipe assembly located in a liquid and having an inlet aperture adapted for the input of a gas/liquid mixture to determine the frequency of sound generated.
  • the pipe assembly may have fixed dimensions. Alternatively, the pipe assembly may have variable dimensions.
  • the liquid in which pipe assembly is located is the same liquid as that used in the gas/liquid mixture.
  • the pipe assembly is constructed of a material which has a density that is very much greater than that of the liquid.
  • the pipe assembly is constructed of a material which has a density that is very much less than that of the liquid.
  • the ratio of gas to liquid in the gas/liquid mixture is less than
  • the bubbles within the gas/liquid mixture may have diameters which are less than 2mm.
  • the apparatus further includes means for supplying the gas/liquid mixture.
  • the means for supplying the gas/liquid mixture may comprise a container in which the gas/liquid mixture is stored under pressure.
  • the means for supplying the gas/liquid mixture may comprise a mixing device which is connected to a source of the gas and the liquid.
  • the means for supplying the gas/liquid mixture may comprise a Venturi device which is connected to a source of the gas and which entrains liquid and mixes it with the gas.
  • the gas may be stored under pressure.
  • the gas/liquid mixture is applied under pressure.
  • the pressure may be less than 10kPa in excess of atmospheric pressure.
  • the volume flow rate of the gas/liquid mixture is less than 10m 3 s "1 .
  • the gas may be air and the liquid may be water. In a sea environment, the liquid may be seawater.
  • a method of producing a frequency variable acoustic signal in a liquid comprising the steps of:- locating a pipe assembly in a liquid; supplying the pipe assembly with a gas/liquid mixture under pressure to generate the acoustic signal at one frequency; and varying the gas/liquid mixture to change the frequency of the acoustic signal generated.
  • Step c) may comprise varying the ratio of gas to liquid in the gas/liquid mixture.
  • step c) may comprise varying the diameter of the bubbles of the gas in the gas/liquid mixture. It is also possible that step c) comprises varying both the ratio of gas to liquid in the gas/liquid mixture and the diameter of the bubbles of the gas in the gas/liquid mixture.
  • the method may include the further step of varying the dimensions of the pipe assembly.
  • a water filled pipe is a classic example of the organ pipe resonance in which the resonant frequency of the pipe is known to be inversely proportional to the length of the pipe and directly proportional to the speed of sound in the pipe.
  • the water in the pipe provides a virtually solid medium which serves only to vary the effective length of the pipe and hence the resonant frequency.
  • the density change is also comparatively small.
  • the change in compressibility is quite significant resulting in a change in the speed of sound within the liquid.
  • a pipe assembly 2 is shown immersed in a liquid 4.
  • the liquid 4 comprises seawater.
  • the pipe assembly 2 can be considered to be identical to an organ pipe assembly whose operation is generally well known.
  • the pipe assembly 2 comprises a pipe 2a which comprises a first portion 2b and a second portion 2c separated by a wall portion 2d.
  • the first portion 2b is smaller in size than the second portion 2c and can be considered to be a pressure reduction chamber.
  • the second portion 2c is open at the end 2e remote from the wall portion 2d and can be considered to be the main body of the pipe 2a.
  • the second portion 2c is a resonating device which generates a sound in accordance with the frequency of a standing wave generated inside it.
  • the standing wave is formed by the reflection of an acoustic wave at the end 2e due to an interface between the inside of the second portion 2c and the surrounding water 4.
  • An inlet 6 is formed in the first portion 2b and an aperture 10 is formed in the second portion 2c.
  • the relationship between the size of the aperture 10 and the diameter of the main body 2c of the pipe 2a determines the frequency of the sound wave generated. This is the same in the present invention, but in this case, it is not air or water which is passed through the pipe 2 to set up the standing wave, but a gas/liquid mixture 8 as will be described in more detail below.
  • the gas/liquid mixture 8 is forced into the pipe 2a through the inlet 6 under pressure and into first portion 2b as indicated by arrow 'A'. Due to the pressure, the gas/liquid mixture 8 is routed through a secondary inlet 12 formed in wall portion 2d and into the second portion 2c of the pipe assembly 2. A standing acoustic wave is developed within the second portion (or main body) 2c of the pipe assembly 2 as described above.
  • the combination of an organ pipe assembly and a bubbly gas/liquid mixture provides an organ type sound generator which, whilst having fixed physical parameters, such as length and diameter, can generate sound having a range of frequencies.
  • the bubbly gas/liquid mixture modifies the speed of sound in the pipe assembly.
  • the frequency can be lowered, relative to the size of the pipe, so that a compact sound source can be made which is smaller than that which can be achieved using existing techniques.
  • the amplitude and frequency of that tone can be continuously variable by modifying the gas/water mixture proportions and the driving pressure. It is thus capable of producing many signal types that are useful in sonar and communications systems such as chirps.
  • the material from which the pipe 2a is made must have a density which is either very much greater than or very much less than water as discussed above. Moreover, it is preferred that the material has a relatively low elastic constant to minimise structural vibrations.
  • Such materials may include, but are not limited to, heavier metals such as lead, iron, copper, gold, natural rocks/minerals, concrete (denser than water), and syntactic foams, double-walled structures containing air/gas (like double glazing) which are lighter than water.
  • air is the gas and seawater is the liquid in the gas/liquid mixture when used in an underwater environment.
  • any other suitable combination of gas and liquid could be used if the apparatus of the present invention is intended to operate in a different liquid environment.
  • the diameter of the bubbles used is less than 2mm and the ratio of air to seawater is less than 1 :100 and is more preferably less than 1 :1000.
  • other suitable bubble diameters and ratios of air to seawater may be used if dictated by a particular application.
  • the pressure and volume flow requirements for the gas/seawater mixture used by the invention are modest - the excess pressure being less than 10kPa (pressure above atmospheric pressure), and the volume flow rate less than 10mV 1 .
  • Venturi device similar to a carburettor
  • gas stored under pressure such as a SCUBA air bottle, for example
  • the pipe assembly in accordance with the present invention may be suspended from a platform on the seabed, floating in the sea or floating on the surface of the sea.
  • the pipe assembly may either have a bubble generator connected directly to it or it may be connected to a remote bubble generator.
  • the bubble generator may be attached to the pipe assembly by any suitable means.
  • further scope for altering the frequency of the sound generated could be provided by having a pipe assembly which has variable dimensions, that is, dimensions that could be varied in use.
  • the pipe assembly in accordance with the present invention requires no electrical or other power supplies, and the gas could be supplied from a pressurised container as described above to provide an entirely independent acoustic source which could be used, for example, as a distress beacon.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Multimedia (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

L'invention se rapporte à une source sonore immergée, qui fait appel à un ensemble tuyau d'orgue (2) alimenté par un mélange gaz/fluide (8). L'ensemble tuyau (2) comprend un tuyau (2a) possédant une première partie et une seconde partie (2b, 2c), séparées par une partie paroi (2d). Le mélange gaz/liquide (8) est introduit dans le tuyau (2) par un orifice d'entrée (6), et, sous l'effet de la pression, est acheminé, à travers un orifice d'entrée secondaire (12) formé dans la partie paroi (2d), jusqu'à la seconde partie (2c) de l'ensemble tuyau (2). La variation du rapport gaz-liquide présenté par le mélange gaz/liquide et/ou du diamètre des bulles de gaz présentes dans le mélange gaz/liquide permet de faire varier la fréquence du son généré, pour un tuyau possédant des dimensions prédéterminées.
PCT/GB2002/004473 2001-10-05 2002-10-02 Source sonore immergee WO2003032012A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0123987.0A GB0123987D0 (en) 2001-10-05 2001-10-05 Underwater sound source
GB0123987.0 2001-10-05

Publications (1)

Publication Number Publication Date
WO2003032012A1 true WO2003032012A1 (fr) 2003-04-17

Family

ID=9923325

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2002/004473 WO2003032012A1 (fr) 2001-10-05 2002-10-02 Source sonore immergee

Country Status (2)

Country Link
GB (1) GB0123987D0 (fr)
WO (1) WO2003032012A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10650931B2 (en) 2017-03-27 2020-05-12 Ge-Hitachi Nuclear Energy Americas Llc Acoustic flowmeters and methods of using the same

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4189026A (en) * 1954-01-13 1980-02-19 The United States Of America As Represented By The Secretary Of The Navy Underwater generation of low frequency sound
US5062089A (en) * 1987-04-17 1991-10-29 Argotec Inc. Sonar projector with liquid mass loading for operation at lower frequency
US5864517A (en) * 1997-03-21 1999-01-26 Adroit Systems, Inc. Pulsed combustion acoustic wave generator
US5999491A (en) * 1995-11-30 1999-12-07 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Low frequency underwater sound source

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4189026A (en) * 1954-01-13 1980-02-19 The United States Of America As Represented By The Secretary Of The Navy Underwater generation of low frequency sound
US5062089A (en) * 1987-04-17 1991-10-29 Argotec Inc. Sonar projector with liquid mass loading for operation at lower frequency
US5999491A (en) * 1995-11-30 1999-12-07 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Low frequency underwater sound source
US5864517A (en) * 1997-03-21 1999-01-26 Adroit Systems, Inc. Pulsed combustion acoustic wave generator

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10650931B2 (en) 2017-03-27 2020-05-12 Ge-Hitachi Nuclear Energy Americas Llc Acoustic flowmeters and methods of using the same

Also Published As

Publication number Publication date
GB0123987D0 (en) 2001-11-28

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