EP1290472A1 - Warning method, system and device based on transmission of acoustic signals - Google Patents

Warning method, system and device based on transmission of acoustic signals

Info

Publication number
EP1290472A1
EP1290472A1 EP01928041A EP01928041A EP1290472A1 EP 1290472 A1 EP1290472 A1 EP 1290472A1 EP 01928041 A EP01928041 A EP 01928041A EP 01928041 A EP01928041 A EP 01928041A EP 1290472 A1 EP1290472 A1 EP 1290472A1
Authority
EP
European Patent Office
Prior art keywords
sonar
reception
antennas
transmission
transmitting
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.)
Withdrawn
Application number
EP01928041A
Other languages
German (de)
French (fr)
Inventor
Marc Brussieux
Jérôme MENIERE
Christophe Migliorini
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.)
Poseidon SA
Original Assignee
Poseidon SA
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 Poseidon SA filed Critical Poseidon SA
Publication of EP1290472A1 publication Critical patent/EP1290472A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • G08B21/02—Alarms for ensuring the safety of persons
    • G08B21/08—Alarms for ensuring the safety of persons responsive to the presence of persons in a body of water, e.g. a swimming pool; responsive to an abnormal condition of a body of water
    • G08B21/082—Alarms for ensuring the safety of persons responsive to the presence of persons in a body of water, e.g. a swimming pool; responsive to an abnormal condition of a body of water by monitoring electrical characteristics of the water
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/06—Systems determining the position data of a target
    • G01S15/08—Systems for measuring distance only
    • G01S15/10—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/539—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Definitions

  • the invention is based on the use of sonars emitting acoustic signals.
  • the object of the invention is to determine certain characteristics of swimmers, in particular swimmers in swimming pools. These characteristics include the absolute position of the swimmer in the volume of water in the pool, their degree of immobility, the amount of air in their lungs.
  • the object of the invention is also to analyze these characteristics and to automatically trigger an alarm system, in particular intended for supervisors or lifeguards, in the event that the situation observed is abnormal.
  • the object of the invention is also to send audible audible messages to an identified swimmer.
  • the subject of the invention is an acoustic detection system, of low cost, of low complexity and of reduced bulk, capable of monitoring swimmers, in particular in public or private swimming pools, to prevent drowning.
  • the subject of the invention is such an acoustic detection system capable of being used in addition to other systems, in particular optical systems.
  • Acoustic detection systems based on the use of sonars, are known for detecting swimmers in difficulty.
  • Such sonars comprise, in a manner known per se, a transmitting antenna which projects acoustic energy into the slice of water to be monitored.
  • a receiver collects the reflected energy, after reflection on bodies moving in this slice and transforms it into electrical signals. Processing means process these signals and the information they convey.
  • the system according to the invention comprises at least one sonar.
  • Each sonar has at least one transmit antenna and one receive antenna having transmit and receive axes.
  • the transmit and receive antennas can in particular be in the form of a single antenna.
  • the sonar is of the parametric sonar type with strong spatial directivity according to the axes of emission and / or reception.
  • the angular opening of the transmitting and / or receiving lobes of said transmitting and / or receiving antennas is of the order of a degree or less than a degree.
  • the transmitting and receiving antennas are intended to deliver acoustic signals and to receive electrical signals or vice versa.
  • the system according to the invention further comprises a processing computer.
  • the sonar further comprises amplification means and transmission means for amplifying and transmitting, to said processing computer, said electrical signals coming from said reception antenna.
  • the sonar may include in addition to amplification means and transmission means for amplifying and transmitting, to said transmitting antenna, the electrical signals coming from said processing computer.
  • the system according to the invention further comprises housings. Each box is fixed to the wall or to the bottom of the pool.
  • the transmit and receive antennas are mounted, inside said boxes, on orientable supports.
  • the transmitting and receiving antennas can in particular be mounted inside the housings which are in the form of hollow ball joints.
  • Each box further comprises orientation means for actuating said orientable supports and for directing said transmission and / or reception axes of said transmission and / or reception antennas in a particular direction of space.
  • the orientation means rotate the ball joints.
  • the system according to the invention comprises modulation means for modulating the acoustic energy emitted by said sonar.
  • the modulation means make it possible to modulate the acoustic energy emitted by said sonar by an audible low frequency signal.
  • the low frequency signal carries in particular a voice message intended for a swimmer.
  • the system according to the invention is such that said transmission and / or reception lobes are coaxial and directed along the transmission and reception axis of said transmission and reception antennas.
  • the orientation means make it possible to simultaneously orient the emission axis and the reception axis of said transmission and reception antennas.
  • the system according to the invention is such that said receiving antennas are connected to said amplification means.
  • the amplification means are located near the receiving antennas.
  • the processing computer activates alert means.
  • the processing computer makes it possible to estimate the amount of air contained in the lungs of a swimmer by comparing said electrical signals received with previously measured signals.
  • the invention also relates to a housing to assist in the prevention of drowning.
  • the housing according to the invention comprises at least one transmitting antenna and one sonar receiving antenna. All or part of the elements making up the sonar are contained inside the housing.
  • the transmit and receive antennas have transmit and receive axes. In the case of certain variant embodiments, they can in particular be in the form of a single antenna.
  • the sonar is of the parametric sonar type with high spatial directivity along said transmission and / or reception axes.
  • the angular opening of the transmission and / or reception lobes of the transmission and / or reception antennas is of the order of a degree or less than a degree.
  • the transmitting and receiving antennas are intended to deliver acoustic signals and to receive electrical signals or vice versa.
  • the electrical signals are intended to be transmitted to a processing computer, via amplification means and transmission means.
  • the boxes are intended to be fixed to the wall or to the bottom of the pool.
  • An enclosure optionally includes orientable supports on which said transmitting and receiving antennas are mounted.
  • the housing is in the form of a hollow ball joint inside which are mounted said transmitting and receiving antennas.
  • a housing also optionally includes orientation means for actuating said orientable supports or said hollow ball joint and for directing said transmission or reception axes of said transmission and reception antennas in a particular direction of space.
  • a housing also optionally includes modulation means for modulating the acoustic energy emitted by said sonar. The modulation means allow 'by modulating a low frequency signal audible acoustic energy emitted by the sonar. The low frequency signal carries in particular a voice message intended for a swimmer.
  • a housing also optionally comprises transmit and receive antennas such that said transmit and / or receive lobes are coaxial and directed along the transmit and receive axis of said transmit and receive antennas.
  • An enclosure also optionally includes amplification means and / or means for transmitting said electrical signals to said processing computer.
  • the invention also relates to a method to assist in the prevention of drowning.
  • the method according to the invention comprises the step of detecting a swimmer and his positioning by using a parametric sonar, with strong spatial directivity, having an angular opening of the emission and / or reception lobes of the order of the degree or less than the degree.
  • the method according to the invention optionally comprises: the step of estimating the degree of mobility of the swimmer, and / or
  • FIG. 1 a partial diagram of the system according to the invention showing the appearance of the primary 117 and secondary 17 transmission lobes of the transmission antennas 2 and the reception lobe 18 of the reception antenna 3, as well as an embodiment of the sonar box fixed to the wall 10 of the swimming pool 12.
  • FIG. 2 a block diagram of the system according to the invention showing the electroacoustic, electronic and mechanical sub-assemblies which compose it.
  • FIG. 3 a schematic representation of the appearance of an alternative embodiment of the high frequency pulse 170 emitted in water and of the low frequency secondary pulse 171 which it generates, after propagation, by non-linear effect in water.
  • the sonar according to the invention shown in FIG. 1 comprises a transmitting antenna 2 formed by an electroacoustic transducer of diameter D and a receiving antenna 3 formed by an electroacoustic transducer.
  • a transmitting antenna 2 formed by an electroacoustic transducer of diameter D
  • a receiving antenna 3 formed by an electroacoustic transducer.
  • Said transmission antennas 2 and reception 3 may be in the form of a single antenna .
  • Sonar 1 is of the parametric sonar type with high spatial directivity along its transmission axis 4 and / or its reception axis 5.
  • the angular opening of the transmission lobes 17 and / or of reception 18 of the transmission antennas 2 and / or receiving 3 are of the order of a degree or less than a degree.
  • the sonar 1 also shows the primary 117 and secondary 17 transmission lobes of the transmission antenna 2 as well as the reception lobe 18 of the reception antenna 3, the description of which will be given below. .
  • Said transmit 2 and receive 3 antennas are intended to transmit acoustic signals in water and to receive electrical signals from a processing computer 6, or vice versa.
  • the sonar 1 also comprises amplification means 7 and transmission means 8 for amplifying and transmitting, to the processing computer 6, the electrical signals coming from the receiving antenna 3.
  • the sonar 1 can also include amplification means 7 and transmission means 8 for amplifying and transmitting, to the transmitting antenna 2, the electrical signals coming from the processing computer 6.
  • the sonar 1 controlled by the processing computer 6 emits a train of high frequency pulses 170 into the water.
  • high frequency is meant frequencies F of the order of magnitude, for example, of 800 kHz.
  • This order of magnitude makes it possible to guarantee that the HF energy of the pulse train 170 in the water remains confined in a narrow primary emission lobe 117 oriented along the emission axis 4.
  • the narrowness of the primary lobe 117 is an important characteristic of the system according to the invention: it allows in particular a better positioning of the swimmer 16 in space and a better rejection of the parasitic reflections 118 of the acoustic energy projected on the surface, the walls 10 and the bottom 11 of the pool 12.
  • Very energetic pulses are used for the emission, such that the pressure emitted is close to the threshold cavitation.
  • One thus generates, in water, after propagation over a distance of approximately 20 to 40 cm, by the known nonlinear effect known as “parametric effect”, a train of low frequency secondary pulses 171 whose energy remains confined in a secondary emission lobe 17.
  • This secondary lobe 17 is, still in known manner, almost as narrow as the primary lobe, that is to say with an angular opening at -3 dB close to the degree.
  • the primary 170 and secondary 171 pulse trains are reflected by the different parts of the body of a swimmer 16, and in particular predominantly by the air trapped in his lungs. It is thus possible to detect the presence of a swimmer 16 located on the transmission 4 and reception 5 axes of the sonar 1. We can also determine if this swimmer 16 has air in his lungs.
  • the receiving antenna 3 converts the reflected acoustic energy into electrical signals. These electrical signals are amplified by the amplification means 7 and transmitted by the transmission means 8 via a connection cable 108 and an interface 109 to the processing computer 6. The electrical signals thus amplified and transmitted are digitized and then processed by the salary calculator 6.
  • the amplification means 7 and transmission 8 of the sonar 1 are located in the immediate vicinity of the reception antenna 3.
  • the signals delivered to the processing computer 6 are of better quality.
  • the amplification 7 and transmission means 8, or amplification and transmission means of the same kind make it possible to amplify and transmit, to the transmission antenna 2, the electrical signals controlled by the processing computer 6.
  • the transmitting antenna 2 converts the electrical signals into acoustic energy.
  • Electronic circuits and / or electroacoustic transducers and / or software enabling the amplification means 7 and transmission means 8 to be produced, as well as the antennas 2, 3 for converting electrical signals into acoustic energy and vice versa, around the threshold cavitation and producing the minimum of distortion, are known per se to those skilled in the art.
  • a sonar the circular emission antenna of which has a diameter of 10 cm, emitting trains of pulses at the frequency of 800 kHz, has a range that exceeds 25 meters.
  • the angular opening of the emission lobe 17 close to one degree, intercepts a circular area with a diameter of the order of 0.5 meters.
  • the electrical signal received by the processing computer 6 contains information concerning the distance from the swimmer 16 measured along the transmission 4 or reception 5 axis. This distance is equal to c times the time between the instant of emission of the impulse of the moment of its reception divided by two (c being the speed of the sound in the water of the swimming pool).
  • This electrical signal also contains information concerning the amount of air contained in the swimmer's lungs 16.
  • the procedure is as follows:
  • - sonar 1 is calibrated by measuring, for any distance between 0 and the maximum range of sonar 1, a standard signal amplitude SI corresponding to the reflection of the pulse emitted by a reference swimmer with lungs full of air
  • - sonar 1 is calibrated by measuring, for any distance between 0 and the maximum range of sonar 1, a standard signal amplitude S2 corresponding to the reflection of the pulse emitted by a reference swimmer with lungs empty of air ,
  • the amplitude of the signal reflected by the swimmer 16 is compared for the distance measured with the amplitudes of the signals S1 and S2 extracted from the calibration table.
  • the pulses emitted can be modulated in different ways.
  • a high frequency pulse 170 consisting of a number of sinusoid arches whose envelope is modulated in 1 + cos ().
  • the shape of the secondary pulse 171 obtained by parametric effect after propagation in water over a certain distance is shown in FIG. 3.
  • the repetition frequency of the pulses 170, 171 is as high as possible. This high repetition frequency makes it possible to measure the successive positions of swimmer 16 in the direction of the receiving axis 5 and to deduce therefrom, with precision, the component, in said direction, of the swimmer movement speed vector 16. This movement speed measurement provides another indication of the state of swimmer 16: an absence of movement which can be considered as a sign of an abnormal situation.
  • a variant of the invention consists in using several sonars 1 placed at different places in the swimming pool 12. It is thus possible to more precisely determine the position of the swimmer 16, in particular by triangulation. It is thus also possible to measure simultaneously the components of the speed vector of the swimmer 16 according to several reception axes 5.
  • the system according to the invention thus also makes it possible to produce a tomographic image of all or part of the submerged area of the swimming pool 12 by systematic scanning in a plurality of directions.
  • the swimming pool 12 is cut into directive exploration slices of its volume of water.
  • Each exploration section is represented in plan by the processing computer 6 by cumulation and juxtaposition of the sonar information obtained by scanning.
  • This tomographic image simplifies the observation of the submerged area of the swimming pool 12 by the bathing supervisor.
  • the frequency of repetition of the pulses 170, 171 can be modulated by an audible signal, for example a voice signal asking the swimmer 16 to return to the surface.
  • an audible signal for example a voice signal asking the swimmer 16 to return to the surface.
  • the energy of the pulses 170, 171 being contained in a transmission lobe 117, 17 of small angular opening, the message is better heard by the swimmer 16 located in the transmission lobe 117, 17 than by the other swimmers located in outside these lobes and at the same distance from the transmitting antenna 2 as the swimmer 16.
  • the directive nature of the emission makes it possible to send a message more particularly audible by the swimmer 16 in difficulty or by a close swimmer who can intervene to his rescue.
  • the system according to the invention is used to provide additional criteria for evaluating the state of a swimmer and to allow doubt to be removed.
  • the transmit 2 and receive 3 antennas are produced so that their transmit 4 and receive 5 axes coincide.
  • the aiming axis of the sonar 1 is both the emission axis 4 and the reception axis 5.
  • This electromechanical assembly is composed of a box 9 fixed to the wall or to the bottom of the swimming pool 12, a transmitting antenna 2, a receiving antenna 3.
  • the housing 9 is produced in the form of a hollow swivel ball joint 20, movably mounted in a housing 90 arranged in the wall 10 or at the bottom 11 of the swimming pool 12.
  • This ball joint 20 is actuated by means of orientation 14 driven by a motor 114.
  • the transmitting antenna 2 and the receiving antenna 3 are mounted inside the hollow ball joint.
  • the diameter D of the electroacoustic emission transducer is chosen so as to facilitate installation in the thickness of the walls 10, 11 of the swimming pool 12. In the case of the variant embodiment described, the diameter D is of the order of 10 centimeters.
  • the transmitting antenna 2 and the receiving antenna 3 are mounted on orientable supports 13 which are themselves movably mounted inside the housing 9. As in the case of the previous embodiment, these orientable supports are actuated by orientation means 14 driven by a motor 114.
  • the housing 9 is fixed inside '' a housing 90 arranged in the wall 10 or at the bottom 11 of the swimming pool 12.
  • the amplification means 7 and transmission 8, as well as the orientation means 14 and the motor 114 are contained in the housing 9 or the ball joint 20.
  • the transmitting 2 and receiving 3 antennas can be oriented so as to automatically scan the submerged area of the swimming pool 12. It is thus possible to produce a tomographic image of all or part with a limited number of sonars 1 of said submerged zone, of the same kind as that previously described and produced by means of a plurality of sonars 1 placed in different locations of the swimming pool 12.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

The invention concerns a warning system to help preventing drowning accidents. The system comprises at least a sonar (1). Each sonar (1) comprises at least a transmission antenna and a reception antenna having transmission (4) and reception (5) apertures. The sonar (1) is a parametric sonar with high spatial directive gain along said transmission (4) and/or reception (5) apertures. The angular opening of the transmission (17) and/or reception (18) lobes of said transmission and/or reception antennae is of the order of one degree or less than one degree. The system comprises a processing calculator. The sonar (1) comprises amplifier means and transmission means for amplifying and transmitting the electric signals coming from said reception antenna.

Description

PROCEDE, SYSTEME ET DISPOSITIF D'ALARME BASE SUR L'EMISSION DE EMISSION BASED ALARM METHOD, SYSTEM AND DEVICE
SIGNAUX ACOUSTIQUESACOUSTIC SIGNALS
L'invention concerne les procédés, les systèmes et les dispositifs d'alarme pour aider à la prévention des noyades. L'invention est basée sur l'utilisation de sonars émettant des signaux acoustiques. L'invention a pour objet de déterminer certaines caractéristiques des nageurs, notamment des nageurs en piscine. Ces caractéristiques sont notamment la position absolue du nageur dans le volume d'eau de la piscine, leur degré d'immobilité, la quantité d'air contenu dans leurs poumons-. L'invention a également pour objet d'analyser ces caractéristiques et de déclencher automatiquement un système d'alarme, notamment à destination de surveillants ou de maîtres-nageurs, dans le cas où la situation constatée est anormale. L'invention a également pour objet d'envoyer à un nageur identifié des messages sonores audibles. L'invention a pour objet un système de détection acoustique, de faible coût, de faible complexité et d'encombrement réduit, capable de surveiller des nageurs, notamment dans des piscines publiques ou privées, pour prévenir les noyades. L'invention a pour objet un tel système de détection acoustique susceptible d'être utilisé en complément d'autres systèmes, notamment optiques. Il est connu des systèmes de détection acoustiques, basés sur l'utilisation de sonars, pour détecter des nageurs en difficulté. De tels sonars comportent, de manière connue en soi, une antenne émettrice qui projette de l'énergie acoustique dans la tranche d'eau à surveiller. Un récepteur capte l'énergie réfléchie, après réflexion sur des corps évoluant dans cette tranche et la transforme en signaux électriques. Des moyens de traitement traitent ces signaux et l'information qu'ils véhiculent. Ces systèmes comportent généralement des antennes directives de dimensions importantes, particulièrement difficiles à installer dans une piscine. La réalisation de ces systèmes est coûteuse. De plus, ces systèmes ne permettent de déterminer avec précision ni la position d'un nageur dans une piscine par rapport à d'autres nageurs ni la quantité d'air contenu dans ses poumons.Disclosed are methods, systems, and alarm devices to assist in the prevention of drowning. The invention is based on the use of sonars emitting acoustic signals. The object of the invention is to determine certain characteristics of swimmers, in particular swimmers in swimming pools. These characteristics include the absolute position of the swimmer in the volume of water in the pool, their degree of immobility, the amount of air in their lungs. The object of the invention is also to analyze these characteristics and to automatically trigger an alarm system, in particular intended for supervisors or lifeguards, in the event that the situation observed is abnormal. The object of the invention is also to send audible audible messages to an identified swimmer. The subject of the invention is an acoustic detection system, of low cost, of low complexity and of reduced bulk, capable of monitoring swimmers, in particular in public or private swimming pools, to prevent drowning. The subject of the invention is such an acoustic detection system capable of being used in addition to other systems, in particular optical systems. Acoustic detection systems, based on the use of sonars, are known for detecting swimmers in difficulty. Such sonars comprise, in a manner known per se, a transmitting antenna which projects acoustic energy into the slice of water to be monitored. A receiver collects the reflected energy, after reflection on bodies moving in this slice and transforms it into electrical signals. Processing means process these signals and the information they convey. These systems generally include large directional antennas, which are particularly difficult to install in a swimming pool. The realization of these systems is expensive. In addition, these systems do not allow precise determination of the position of a swimmer in a pool relative to other swimmers or the amount of air contained in his lungs.
L'invention concerne un système d'alarme pour aider à la prévention des noyades. Le système selon l'invention comprend au moins un sonar. Chaque sonar comporte au moins une antenne d'émission et une antenne de réception ayant des axes d'émission et de réception. Dans une variante de réalisation de l'invention, les antennes d'émission et de réception peuvent notamment se présenter sous la forme d'une seule antenne. Le sonar est du type sonar paramétrique à forte directivité spatiale selon les axes d'émission et/ou de réception. L'ouverture angulaire des lobes d'émission et/ou de réception desdites antennes d'émission et/ou de réception est de l'ordre du degré ou inférieure au degré. Les antennes d'émission et de réception sont destinées à délivrer des signaux acoustiques et à recevoir des signaux électriques ou inversement. Le système selon 1 ' invention comprend en outre un calculateur de traitement. Le sonar comporte en outre des moyens d'amplification et des moyens de transmission pour amplifier et transmettre, vers ledit calculateur de traitement, lesdits signaux électriques provenant de ladite antenne de réception. Dans une variante de réalisation, le sonar peut comporter en outre des moyens d'amplification et des moyens de transmission pour amplifier et transmettre, vers ladite antenne d'émission, les signaux électriques provenant dudit calculateur de traitement . De préférence, le système selon l'invention comprend en outre des boîtiers. Chaque boîtier est fixé au mur ou au fond de la piscine. Dans ce cas, les antennes d'émission et de réception sont montées, à l'intérieur desdits boîtiers, sur des supports orientables. Les antennes d'émission et de réception peuvent notamment être montées l'intérieur des boîtiers se présentant sous la forme de rotules creuses. Chaque boîtier comporte en outre des moyens d'orientation pour actionner lesdits supports orientables et pour diriger lesdits axes d'émission et/ou de réception desdites antennes d'émission et/ou de réception dans une direction particulière de l'espace. Dans le cas où les boîtiers se présentent sous la forme de rotules creuses, les moyens d'orientation actionnent en rotation les rotules .An alarm system to assist in the prevention of drowning is disclosed. The system according to the invention comprises at least one sonar. Each sonar has at least one transmit antenna and one receive antenna having transmit and receive axes. In an alternative embodiment of the invention, the transmit and receive antennas can in particular be in the form of a single antenna. The sonar is of the parametric sonar type with strong spatial directivity according to the axes of emission and / or reception. The angular opening of the transmitting and / or receiving lobes of said transmitting and / or receiving antennas is of the order of a degree or less than a degree. The transmitting and receiving antennas are intended to deliver acoustic signals and to receive electrical signals or vice versa. The system according to the invention further comprises a processing computer. The sonar further comprises amplification means and transmission means for amplifying and transmitting, to said processing computer, said electrical signals coming from said reception antenna. In an alternative embodiment, the sonar may include in addition to amplification means and transmission means for amplifying and transmitting, to said transmitting antenna, the electrical signals coming from said processing computer. Preferably, the system according to the invention further comprises housings. Each box is fixed to the wall or to the bottom of the pool. In this case, the transmit and receive antennas are mounted, inside said boxes, on orientable supports. The transmitting and receiving antennas can in particular be mounted inside the housings which are in the form of hollow ball joints. Each box further comprises orientation means for actuating said orientable supports and for directing said transmission and / or reception axes of said transmission and / or reception antennas in a particular direction of space. In the case where the housings are in the form of hollow ball joints, the orientation means rotate the ball joints.
De préférence également, le système selon l'invention comprend des moyens de modulation pour moduler l'énergie acoustique émise par ledit sonar. Les moyens de modulation permettent de moduler par un signal basse fréquence audible l'énergie acoustique émise par ledit sonar. Le signal basse fréquence porte notamment un message vocal à destination d'un nageur.Preferably also, the system according to the invention comprises modulation means for modulating the acoustic energy emitted by said sonar. The modulation means make it possible to modulate the acoustic energy emitted by said sonar by an audible low frequency signal. The low frequency signal carries in particular a voice message intended for a swimmer.
De préférence également, le système selon l'invention est tel que lesdits lobes d'émission et/ou de réception sont coaxiaux et dirigés selon l'axe d'émission et de réception desdites antennes d'émission et de réception. Ainsi, les moyens d'orientation permettent d'orienter simultanément l'axe d'émission et l'axe de réception desdites antennes d'.émission et de réception.Preferably also, the system according to the invention is such that said transmission and / or reception lobes are coaxial and directed along the transmission and reception axis of said transmission and reception antennas. Thus, the orientation means make it possible to simultaneously orient the emission axis and the reception axis of said transmission and reception antennas.
De . préférence également, le système selon 1 ' invention est tel que lesdites antennes de réception sont connectées auxdits moyens d'amplification. Avantageusement dans ce cas, les moyens d'amplification sont situés à proximité des antennes de réception. Ainsi, le signal amplifié délivré audit calculateur de traitement est de meilleure qualité.From. preferably also, the system according to the invention is such that said receiving antennas are connected to said amplification means. Advantageously in this case, the amplification means are located near the receiving antennas. Thus, the amplified signal delivered to said processing computer is of better quality.
De préférence, afin d'aider à la prévention des noyades, notamment dans une piscine, le calculateur de traitement active des moyens d'alerte. Avantageusement, le calculateur de traitement permet d'estimer la quantité d'air contenue dans les poumons d'un nageur en comparant lesdits signaux électriques reçus à des signaux préalablement mesurés. L'invention concerne également un boîtier destiné à aider à la prévention des noyades . Le boîtier selon 1 ' invention comporte au moins une antenne d'émission et une antenne de réception d'un sonar. Tout ou partie des éléments composant le sonar sont contenus à l'intérieur du boîtier. Les antennes d'émission et de réception ont des axes d'émission et de réception. Dans le cas de certaines variantes de réalisation, elles peuvent notamment se présenter sous la forme d'une seule antenne. Le sonar est du type sonar paramétrique à forte directivité spatiale selon lesdits axes d'émission et/ou de réception. L'ouverture angulaire des lobes d'émission et/ou de réception des antennes d'émission et/ou de réception est de l'ordre du degré ou inférieure au degré. Les antennes d'émission et de réception sont destinées à délivrer des signaux acoustiques et à recevoir des signaux électriques ou inversement. Les signaux électriques sont destinés à être transmis à un calculateur de traitement, via des moyens d'amplification et des moyens de transmission. Les boîtiers sont destinés à être fixés au mur ou au fond de la piscine. Un boîtier comprend de manière optionnelle des supports orientables sur lesquels sont montées lesdites antennes d'émission et de réception. Dans le cas de certaines variantes de réalisation le boîtier se présente sous la forme d'une rotule creuse à l'intérieur de laquelle sont montées lesdites antennes d'émission et de réception. Un boîtier comprend également de manière optionnelle des moyens d'orientation pour actionner lesdits supports orientables ou ladite rotule creuse et pour diriger lesdits axes d'émission ou de réception desdites antennes d'émission et de réception dans une direction particulière de 1 'espace . Un boîtier comprend également de manière optionnelle des moyens de modulation pour moduler l'énergie acoustique émise par ledit sonar. Les moyens de modulation permettent de ' moduler par un signal basse fréquence audible l'énergie acoustique émise par le sonar. Le signal basse fréquence porte notamment un message vocal à destination d'un nageur. Un boîtier comprend également de manière optionnelle des antennes d'émission et de réception telles que lesdits lobes d'émission et/ou de réception sont coaxiaux et dirigés selon l'axe d'émission et de réception desdites antennes d'émission et de réception. Un boîtier comprend également de manière optionnelle des moyens d'amplification et/ou des moyens de transmission desdits signaux électriques vers ledit calculateur de traitement.Preferably, in order to help prevent drowning, especially in a swimming pool, the processing computer activates alert means. Advantageously, the processing computer makes it possible to estimate the amount of air contained in the lungs of a swimmer by comparing said electrical signals received with previously measured signals. The invention also relates to a housing to assist in the prevention of drowning. The housing according to the invention comprises at least one transmitting antenna and one sonar receiving antenna. All or part of the elements making up the sonar are contained inside the housing. The transmit and receive antennas have transmit and receive axes. In the case of certain variant embodiments, they can in particular be in the form of a single antenna. The sonar is of the parametric sonar type with high spatial directivity along said transmission and / or reception axes. The angular opening of the transmission and / or reception lobes of the transmission and / or reception antennas is of the order of a degree or less than a degree. The transmitting and receiving antennas are intended to deliver acoustic signals and to receive electrical signals or vice versa. The electrical signals are intended to be transmitted to a processing computer, via amplification means and transmission means. The boxes are intended to be fixed to the wall or to the bottom of the pool. An enclosure optionally includes orientable supports on which said transmitting and receiving antennas are mounted. In the case of certain variant embodiments, the housing is in the form of a hollow ball joint inside which are mounted said transmitting and receiving antennas. A housing also optionally includes orientation means for actuating said orientable supports or said hollow ball joint and for directing said transmission or reception axes of said transmission and reception antennas in a particular direction of space. A housing also optionally includes modulation means for modulating the acoustic energy emitted by said sonar. The modulation means allow 'by modulating a low frequency signal audible acoustic energy emitted by the sonar. The low frequency signal carries in particular a voice message intended for a swimmer. A housing also optionally comprises transmit and receive antennas such that said transmit and / or receive lobes are coaxial and directed along the transmit and receive axis of said transmit and receive antennas. An enclosure also optionally includes amplification means and / or means for transmitting said electrical signals to said processing computer.
L'invention concerne également un procédé pour aider à la prévention des noyades . Le procédé selon 1 ' invention comprend l'étape de détecter un nageur et son positionnement en mettant en oeuvre un sonar paramétrique, à forte directivité spatiale, ayant une ouverture angulaire des lobes d'émission et/ou de réception de l'ordre du degré ou inférieure au degré. Le procédé selon l'invention comprend en option : - l'étape d'estimer le degré de mobilité du nageur, et/ouThe invention also relates to a method to assist in the prevention of drowning. The method according to the invention comprises the step of detecting a swimmer and his positioning by using a parametric sonar, with strong spatial directivity, having an angular opening of the emission and / or reception lobes of the order of the degree or less than the degree. The method according to the invention optionally comprises: the step of estimating the degree of mobility of the swimmer, and / or
- l'étape d'estimer la quantité d'air restant dans les poumons dudit nageur, et/outhe step of estimating the quantity of air remaining in the lungs of said swimmer, and / or
- l'étape d'émettre vers ledit nageur des signaux audibles au moyen dudit sonar paramétrique.the step of transmitting audible signals to said swimmer by means of said parametric sonar.
L'invention concerne également l'utilisation d'un sonar paramétrique, à forte directivité spatiale, ayant une ouverture angulaire des lobes d'émission et/ou de réception de l'ordre du degré ou inférieure au degré, dans un système de prévention des noyades. D'autres particularités et avantages de l'invention apparaîtront clairement dans la description suivante présentée à titre d'exemple non limitatif en regard des figures annexées qui représentent : La figure 1 : un schéma partiel du système selon l'invention montrant l'allure des lobes d'émission primaire 117 et secondaire 17 des antennes d'émission 2 et du lobe de réception 18 de l'antenne de réception 3, ainsi qu'une forme de réalisation du boîtier sonar fixé au mur 10 de la piscine 12. La figure 2 : un schéma de principe du système selon l'invention montrant les sous-ensembles électroacoustique, électronique et mécanique qui le composent.The invention also relates to the use of a parametric sonar, with strong spatial directivity, having an angular opening of the emission and / or reception lobes of the order of the degree or less than the degree, in a system for preventing drowning. Other features and advantages of the invention will appear clearly in the following description presented by way of nonlimiting example with reference to the appended figures which represent: FIG. 1: a partial diagram of the system according to the invention showing the appearance of the primary 117 and secondary 17 transmission lobes of the transmission antennas 2 and the reception lobe 18 of the reception antenna 3, as well as an embodiment of the sonar box fixed to the wall 10 of the swimming pool 12. FIG. 2: a block diagram of the system according to the invention showing the electroacoustic, electronic and mechanical sub-assemblies which compose it.
La figure 3 : une représentation schématique de l'allure d'une variante de réalisation de l'impulsion haute fréquence 170 émise dans l'eau et de l'impulsion secondaire basse fréquence 171 qu'elle engendre, après propagation, par effet non linéaire dans l'eau.FIG. 3: a schematic representation of the appearance of an alternative embodiment of the high frequency pulse 170 emitted in water and of the low frequency secondary pulse 171 which it generates, after propagation, by non-linear effect in water.
Le sonar selon 1 ' invention représenté sur la figure 1 comporte une antenne d'émission 2 formée d'un transducteur électroacoustique de diamètre D et une antenne de réception 3 formée d'un transducteur électroacoustique. Sur la figure 1, on a représenté les axes d'émission 4 et de réception 5 desdites antennes d'émission 2 et de réception 3. Lesdites antennes d'émission 2 et de réception 3 peuvent se présenter sous la forme d'une seule antenne. Le sonar 1 est du type sonar paramétrique à forte directivité spatiale selon son axe d'émission 4 et/ou son axe de réception 5. L'ouverture angulaire des lobes d'émission 17 et/ou de réception 18 des antennes d'émission 2 et/ou de réception 3 sont de l'ordre du degré ou inférieure au degré. On a également représenté sur la figure 1 les lobes d'émission primaire 117 et secondaire.17 de l'antenne d'émission 2 ainsi que le lobe de réception 18 de l'antenne de réception 3, dont la description sera ci-après précisée. Lesdites antennes d'émission 2 et de réception 3 sont destinées à émettre des signaux acoustiques dans l'eau et à recevoir des signaux électriques d'un calculateur de traitement 6, ou inversement. A cet effet, le sonar 1 comporte en outre des moyens d'amplification 7 et des moyens de transmission 8 pour amplifier et transmettre, vers le calculateur de traitement 6, les signaux électriques provenant de 1 ' antenne de réception 3. Dans une autre variante de réalisation, le sonar 1 peut en outre comporter des moyens d'amplification 7 et des moyens de transmission 8 pour amplifier et transmettre, vers l'antenne d'émission 2, les signaux électriques provenant du calculateur de traitement 6.The sonar according to the invention shown in FIG. 1 comprises a transmitting antenna 2 formed by an electroacoustic transducer of diameter D and a receiving antenna 3 formed by an electroacoustic transducer. In Figure 1, there is shown the transmission axes 4 and reception 5 of said transmission antennas 2 and reception 3. Said transmission antennas 2 and reception 3 may be in the form of a single antenna . Sonar 1 is of the parametric sonar type with high spatial directivity along its transmission axis 4 and / or its reception axis 5. The angular opening of the transmission lobes 17 and / or of reception 18 of the transmission antennas 2 and / or receiving 3 are of the order of a degree or less than a degree. FIG. 1 also shows the primary 117 and secondary 17 transmission lobes of the transmission antenna 2 as well as the reception lobe 18 of the reception antenna 3, the description of which will be given below. . Said transmit 2 and receive 3 antennas are intended to transmit acoustic signals in water and to receive electrical signals from a processing computer 6, or vice versa. To this end, the sonar 1 also comprises amplification means 7 and transmission means 8 for amplifying and transmitting, to the processing computer 6, the electrical signals coming from the receiving antenna 3. In another variant In one embodiment, the sonar 1 can also include amplification means 7 and transmission means 8 for amplifying and transmitting, to the transmitting antenna 2, the electrical signals coming from the processing computer 6.
On va maintenant décrire comment fonctionne le système selon l'invention. Le sonar 1 contrôlé par le calculateur de traitement 6 émet un train d'impulsions haute fréquence 170 dans l'eau. On entend par haute fréquence des fréquences F de l'ordre de grandeur, à titre d'exemple, de 800 kHz. Cet ordre de grandeur permet de garantir que 1 ' énergie HF du train d-' impulsion 170 dans l'eau reste confinée dans un lobe primaire d'émission 117 étroit orienté selon l'axe d'émission 4. L'étroitesse du lobe primaire d'émission 117 est une caractéristique importante du système selon l'invention : elle permet notamment un meilleur positionnement du nageur 16 dans l'espace et une meilleure réjection des réflexions parasites 118 de l'énergie acoustique projetée sur la surface, les murs 10 et le fond 11 de la piscine 12. En champ lointain, l'ouverture angulaire A (exprimée en radians) du lobe d'émission à -3 dB d'une antenne d'émission circulaire de diamètre D (exprimé en mètres) à une fréquence FWe will now describe how the system according to the invention works. The sonar 1 controlled by the processing computer 6 emits a train of high frequency pulses 170 into the water. By high frequency is meant frequencies F of the order of magnitude, for example, of 800 kHz. This order of magnitude makes it possible to guarantee that the HF energy of the pulse train 170 in the water remains confined in a narrow primary emission lobe 117 oriented along the emission axis 4. The narrowness of the primary lobe 117 is an important characteristic of the system according to the invention: it allows in particular a better positioning of the swimmer 16 in space and a better rejection of the parasitic reflections 118 of the acoustic energy projected on the surface, the walls 10 and the bottom 11 of the pool 12. In the far field, the angular opening A (expressed in radians) of the emission lobe at -3 dB from a circular emission antenna of diameter D (expressed in meters) at a frequency F
(exprimée en Hz) est de manière connue donnée par la formule :(expressed in Hz) is in known manner given by the formula:
A = c/(D.F), où c est la célérité (exprimée en m/s) des ondes acoustiques dans le milieu considéré. Ainsi, par exemple, pour une antenne d'émission circulaire de diamètre D≈lOcrn et une fréquence F=800 kHz, l'ouverture angulaire A est voisine du degré.A = c / (D.F), where c is the speed (expressed in m / s) of the acoustic waves in the medium considered. Thus, for example, for a circular transmitting antenna of diameter D≈lOcrn and a frequency F = 800 kHz, the angular opening A is close to the degree.
On utilise pour l'émission des impulsions très énergétiques, telles que la pression émise soit proche du seuil de cavitation. On engendre ainsi, dans l'eau, après propagation sur une distance d'environ 20 à 40 cm, par l'effet non linéaire connu dit « effet paramétrique », un train d'impulsions secondaires basse fréquence 171 dont l'énergie reste confinée dans un lobe secondaire d'émission 17. Ce lobe secondaire 17 est, toujours de manière connue, quasiment aussi étroit que le lobe primaire, c'est à dire d'ouverture angulaire à -3 dB proche du degré.Very energetic pulses are used for the emission, such that the pressure emitted is close to the threshold cavitation. One thus generates, in water, after propagation over a distance of approximately 20 to 40 cm, by the known nonlinear effect known as “parametric effect”, a train of low frequency secondary pulses 171 whose energy remains confined in a secondary emission lobe 17. This secondary lobe 17 is, still in known manner, almost as narrow as the primary lobe, that is to say with an angular opening at -3 dB close to the degree.
Cet effet paramétrique est notamment décrit dans la thèse ayant pour titre « Contribution Théorique et Expérimentale à l'Etude de l'Emission et de la Réception Paramétriques » soutenue par M. Pierre Cervenka le 17 mars 1988 à l'université Pierre et Marie Curie Paris 6 à Paris ; cette thèse a pour référence dans la base de données de l'INIST : Th. ; 88 PAO6 6127, Cote INIST : TD 19209. Cet effet paramétrique est également décrit dans les articles et ouvrages suivants : (a) P.J. Westervelt, "Parametric acoustic array", JASA (Journal of the Acoustical Society of America) vol. 35 n°4, p. 535-537, 1963 ; (b) H.O. Berktay, "Parametric amplification by the use of acoustic non linearities and some possible applications",This parametric effect is described in particular in the thesis entitled "Theoretical and Experimental Contribution to the Study of Parametric Emission and Reception" presented by M. Pierre Cervenka on March 17, 1988 at the Pierre and Marie Curie University of Paris 6 in Paris; this thesis is referenced in the INIST database: Th.; 88 PAO6 6127, INIST code: TD 19209. This parametric effect is also described in the following articles and works: (a) P.J. Westervelt, "Parametric acoustic array", JASA (Journal of the Acoustical Society of America) vol. 35 n ° 4, p. 535-537, 1963; (b) H.O. Berktay, "Parametric amplification by the use of acoustic non linearities and some possible applications",
Journal of Sound and Vibrations, vol. 2 n°4, p.462, 1965 ; (c)Journal of Sound and Vibrations, vol. 2 no 4, p. 462, 1965; (vs)
M.B. Moffett and R.H. Mellen "Nearfield characteristics of parametric acoustic sources", JASA vol.69 n°2 p.404-409 (1981) ;M.B. Moffett and R.H. Mellen "Nearfield characteristics of parametric acoustic sources", JASA vol.69 n ° 2 p.404-409 (1981);
(d) M.B. Moffett and R.H. Mellen "Effective lengths of parametric acoustic sources", JASA vol.70 n°5. p.1424-1426(d) M.B. Moffett and R.H. Mellen "Effective lengths of parametric acoustic sources", JASA vol.70 n ° 5. p.1424-1426
(1981) ; (e) "Nonlinear Underater Acoustics" de B.K. Novikov,(nineteen eighty one) ; (e) "Nonlinear Underater Acoustics" by B.K. Novikov,
O.V. Rudenko et V.I. Timoshenko, publié pour l'ASA (AcousticalO.V. Rudenko and V.I. Timoshenko, published for the ASA (Acoustical
Society of America) par le "American Institute of Physics"Society of America) by the "American Institute of Physics"
(1987) . Les trains d'impulsions primaire 170 et secondaire 171 sont réfléchis par les différentes parties du corps d'un nageur 16, et notamment de manière prépondérante par l'air emprisonné dans ses poumons. On peut ainsi détecter la présence d'un nageur 16 situé sur les axes d'émission 4 et de réception 5 du sonar 1. On peut ainsi aussi déterminer si ce nageur 16 a de l'air dans ses poumons.(1987). The primary 170 and secondary 171 pulse trains are reflected by the different parts of the body of a swimmer 16, and in particular predominantly by the air trapped in his lungs. It is thus possible to detect the presence of a swimmer 16 located on the transmission 4 and reception 5 axes of the sonar 1. We can also determine if this swimmer 16 has air in his lungs.
La fraction de l'énergie des impulsions primaires et secondaires réfléchie par le corps du nageur 16, revient vers l'antenne de réception 3.The fraction of the energy of the primary and secondary pulses reflected by the body of the swimmer 16, returns to the receiving antenna 3.
L'antenne de réception 3 convertit l'énergie acoustique réfléchie en signaux électriques. Ces signaux électriques sont amplifiés par les moyens d'amplification 7 et transmis par les moyens de transmission 8 via un câble de liaison 108 et une interface 109 vers le calculateur de traitement 6. Les signaux électriques ainsi amplifiés et transmis sont numérisés puis traités par le calculateur de traitement 6.The receiving antenna 3 converts the reflected acoustic energy into electrical signals. These electrical signals are amplified by the amplification means 7 and transmitted by the transmission means 8 via a connection cable 108 and an interface 109 to the processing computer 6. The electrical signals thus amplified and transmitted are digitized and then processed by the salary calculator 6.
Avantageusement, les moyens d'amplification 7 et de transmission 8 du sonar 1 sont situés à proximité immédiate de l'antenne de réception 3. Ainsi les signaux délivrés au calculateur de traitement 6 sont de meilleure qualité.Advantageously, the amplification means 7 and transmission 8 of the sonar 1 are located in the immediate vicinity of the reception antenna 3. Thus the signals delivered to the processing computer 6 are of better quality.
Avantageusement également, les moyens d'amplification 7 et de transmission 8, ou des moyens d'amplification et de transmission de même nature, permettent d'amplifier et de transmettre, vers l'antenne d'émission 2, les signaux électriques contrôlés par le calculateur de traitement 6. L'antenne d'émission 2 convertit les signaux électriques en énergie acoustique.Advantageously also, the amplification 7 and transmission means 8, or amplification and transmission means of the same kind, make it possible to amplify and transmit, to the transmission antenna 2, the electrical signals controlled by the processing computer 6. The transmitting antenna 2 converts the electrical signals into acoustic energy.
Les circuits électroniques et/ou les transducteurs électroacoustiques et/ou les logiciels permettant de réaliser les moyens d'amplification 7 et de transmission 8, ainsi que les antennes 2, 3 de conversion des signaux électriques en énergie acoustique et réciproquement, en avoisinant le seuil de cavitation et en produisant le minimum de distorsion, sont en soi connus de l'homme de métier.Electronic circuits and / or electroacoustic transducers and / or software enabling the amplification means 7 and transmission means 8 to be produced, as well as the antennas 2, 3 for converting electrical signals into acoustic energy and vice versa, around the threshold cavitation and producing the minimum of distortion, are known per se to those skilled in the art.
A titre d'illustration d'une variante de réalisation de l'invention, il est ici précisé qu'un sonar, dont l'antenne d'émission circulaire a un diamètre de 10 cm, émettant des trains d'impulsions à la fréquence de 800 kHz, a une portée qui dépasse 25 mètres. A cette distance, l'ouverture angulaire du lobe d'émission 17, voisine de un degré, intercepte une zone circulaire de diamètre de l'ordre de 0,5 mètre.By way of illustration of an alternative embodiment of the invention, it is here specified that a sonar, the circular emission antenna of which has a diameter of 10 cm, emitting trains of pulses at the frequency of 800 kHz, has a range that exceeds 25 meters. At this distance, the angular opening of the emission lobe 17, close to one degree, intercepts a circular area with a diameter of the order of 0.5 meters.
Le signal électrique reçu par le calculateur de traitement 6 contient des informations concernant la distance du nageur 16 mesurée le long de l'axe d'émission 4 ou de réception 5. Cette distance est égale à c fois le temps séparant l'instant d'émission de l'impulsion de l'instant de sa réception divisé par deux (c étant la célérité du son dans l'eau de la piscine) .The electrical signal received by the processing computer 6 contains information concerning the distance from the swimmer 16 measured along the transmission 4 or reception 5 axis. This distance is equal to c times the time between the instant of emission of the impulse of the moment of its reception divided by two (c being the speed of the sound in the water of the swimming pool).
Ce signal électrique contient également des infor- mations concernant la quantité d'air contenue dans les poumons du nageur 16. De préférence, pour mesurer cette quantité d'air, on procède de la manière suivante :This electrical signal also contains information concerning the amount of air contained in the swimmer's lungs 16. Preferably, to measure this amount of air, the procedure is as follows:
- on calibre le sonar 1 en mesurant, pour toute distance comprise entre 0 et la portée maximale du sonar 1, une amplitude de signal SI standard correspondant à la réflexion de 1 ' impulsion émise par un nageur de référence ayant les poumons pleins d'air- sonar 1 is calibrated by measuring, for any distance between 0 and the maximum range of sonar 1, a standard signal amplitude SI corresponding to the reflection of the pulse emitted by a reference swimmer with lungs full of air
- on calibre le sonar 1 en mesurant, pour toute distance comprise entre 0 et la portée maximale du sonar 1, une amplitude de signal S2 standard correspondant à la réflexion de l'impulsion émise par un nageur de référence ayant les poumons vides d'air,- sonar 1 is calibrated by measuring, for any distance between 0 and the maximum range of sonar 1, a standard signal amplitude S2 corresponding to the reflection of the pulse emitted by a reference swimmer with lungs empty of air ,
- on reporte les amplitudes SI et S2 en fonction de la distance dans un tableau de calibration, - on détermine simultanément la distance du nageur 16 par rapport aux antennes d'émission 2 et de réception 3 et l'amplitude du signal réfléchi par celui-ci,- the amplitudes SI and S2 are reported as a function of the distance in a calibration table, - the distance of the swimmer 16 relative to the transmit 2 and receive 3 antennas and the amplitude of the signal reflected by it are simultaneously determined this,
- on compare, pour la distance mesurée, l'amplitude du signal réfléchi par le nageur 16 aux amplitudes des signaux SI et S2 extraits du tableau de calibration.- The amplitude of the signal reflected by the swimmer 16 is compared for the distance measured with the amplitudes of the signals S1 and S2 extracted from the calibration table.
- on en déduit une estimation de la quantité d'air restant dans les poumons du nageur 16.- we deduce an estimate of the amount of air remaining in the swimmer's lungs 16.
Cette mesure, bien qu'imprécise, peut entrer dans la liste de critères utilisés par le calculateur, de traitement 6 pour donner l'alarme. Sans changer les traits techniques essentiels de l'invention, on peut moduler de différentes façons les impulsions émises. On peut émettre par exemple, comme représenté, a titre purement schématique et non limitatif, une impulsion haute fréquence 170, constituée d'un certain nombre d'arches de sinusoïde dont 1 'enveloppe est modulée en 1+cos () . Dans le cas de cette modulation particulière, l'allure de l'impulsion secondaire 171 obtenue par effet paramétrique après propagation dans l'eau sur une certaine distance est représentée sur la figure 3.This measurement, although imprecise, can enter the list of criteria used by the computer, processing 6 to give the alarm. Without changing the essential technical features of the invention, the pulses emitted can be modulated in different ways. One can emit for example, as shown, purely schematically and without limitation, a high frequency pulse 170, consisting of a number of sinusoid arches whose envelope is modulated in 1 + cos (). In the case of this particular modulation, the shape of the secondary pulse 171 obtained by parametric effect after propagation in water over a certain distance is shown in FIG. 3.
La fréquence de répétition des impulsions 170, 171 est la plus élevée possible. Cette fréquence de répétition élevée permet de mesurer les positions successives du nageur 16 dans la direction de l'axe de réception 5 et d'en déduire, avec précision, la composante, selon ladite direction, du vecteur vitesse de déplacement du nageur 16. Cette mesure de vitesse de déplacement fournit une autre indication quant à l'état du nageur 16 : une absence de mouvement pouvant être considérée comme un signe de situation anormale. Une variante de l'invention consiste à utiliser plusieurs sonars 1 disposés à différents endroits de la piscine 12. Il est ainsi possible de déterminer avec davantage de précision la position du nageur 16, notamment par triangulation. Il est ainsi également possible de mesurer simultanément les composantes du vecteur vitesse du nageur 16 selon plusieurs axes de réception 5. Dans le cas de l'utilisation d'au moins trois antennes de réception 3, on peut ainsi reconstituer par traitement de l'information le vecteur vitesse du nageur 16. Le système selon l'invention permet ainsi également de réaliser une image tomographique de tout ou partie de la zone submergée de la piscine 12 par balayage systématique dans une pluralité de directions. On découpe la piscine 12 en tranches d'exploration directive de son volume d'eau. Chaque tranche d'exploration est représentée en plan par le calculateur de traitement 6 par cumul et juxtaposition des informations sonar obtenues par balayage. Cette image tomographique simplifie l'observation de la zone submergée de la piscine 12 par le surveillant de baignade.The repetition frequency of the pulses 170, 171 is as high as possible. This high repetition frequency makes it possible to measure the successive positions of swimmer 16 in the direction of the receiving axis 5 and to deduce therefrom, with precision, the component, in said direction, of the swimmer movement speed vector 16. This movement speed measurement provides another indication of the state of swimmer 16: an absence of movement which can be considered as a sign of an abnormal situation. A variant of the invention consists in using several sonars 1 placed at different places in the swimming pool 12. It is thus possible to more precisely determine the position of the swimmer 16, in particular by triangulation. It is thus also possible to measure simultaneously the components of the speed vector of the swimmer 16 according to several reception axes 5. In the case of the use of at least three reception antennas 3, it is thus possible to reconstruct by information processing the speed vector of the swimmer 16. The system according to the invention thus also makes it possible to produce a tomographic image of all or part of the submerged area of the swimming pool 12 by systematic scanning in a plurality of directions. The swimming pool 12 is cut into directive exploration slices of its volume of water. Each exploration section is represented in plan by the processing computer 6 by cumulation and juxtaposition of the sonar information obtained by scanning. This tomographic image simplifies the observation of the submerged area of the swimming pool 12 by the bathing supervisor.
Dans un mode de fonctionnement particulier du système selon l'invention, la fréquence de répétition des impulsions 170, 171 peut être modulée par un signal audible, par exemple un signal vocal demandant au nageur 16 de remonter à la surface. L'énergie des impulsions 170, 171 étant contenue dans un lobe d'émission 117, 17 de faible ouverture angulaire, le message est mieux entendu par le nageur 16 situé dans le lobe d'émission 117, 17 que par les autres nageurs situés en dehors de ces lobes et à la même distance de l'antenne d'émission 2 que le nageur 16. Le caractère directif de l'émission permet d'envoyer un message plus particulièrement audible par le nageur 16 en difficulté ou par un nageur proche pouvant intervenir à son secours.In a particular mode of operation of the system according to the invention, the frequency of repetition of the pulses 170, 171 can be modulated by an audible signal, for example a voice signal asking the swimmer 16 to return to the surface. The energy of the pulses 170, 171 being contained in a transmission lobe 117, 17 of small angular opening, the message is better heard by the swimmer 16 located in the transmission lobe 117, 17 than by the other swimmers located in outside these lobes and at the same distance from the transmitting antenna 2 as the swimmer 16. The directive nature of the emission makes it possible to send a message more particularly audible by the swimmer 16 in difficulty or by a close swimmer who can intervene to his rescue.
Dans une variante de réalisation mettant en oeuvre des caméras optiques pour surveiller une piscine, on utilise le système selon l'invention pour apporter des critères complémentaires d'évaluation de l'état d'un nageur et permettre une levée de doute.In an alternative embodiment using optical cameras to monitor a swimming pool, the system according to the invention is used to provide additional criteria for evaluating the state of a swimmer and to allow doubt to be removed.
Selon une variante de réalisation du système selon l'invention, on réalise les antennes d'émission 2 et de réception 3 de telle sorte que leurs axes d'émission 4 et de réception 5 coïncident. Ainsi l'axe de visée du sonar 1 est à la fois l'axe d'émission 4 et l'axe de réception 5.According to an alternative embodiment of the system according to the invention, the transmit 2 and receive 3 antennas are produced so that their transmit 4 and receive 5 axes coincide. Thus the aiming axis of the sonar 1 is both the emission axis 4 and the reception axis 5.
On va maintenant décrire une variante de réalisation de l'ensemble électromécanique dans lequel tout ou partie du sonar 1 est monté. Cet ensemble électromécanique est composé d'un boîtier 9 fixé au mur ou au fond de la piscine 12, d'une antenne d'émission 2, d'une antenne de réception 3. Dans le cas de la variante de réalisation représentée sur la figure 1, le boîtier 9 est réalisé sous la forme d'une rotule 20 creuse, orientable, monté de manière mobile dans un logement 90 aménagé dans le mur 10 ou au fond 11 de la piscine 12. Cette rotule 20 est actionnée par des moyens d'orientation 14 mus par un moteur 114. Dans le cas de cette variante de réalisation, l'antenne d'émission 2 et l'antenne de réception 3 sont montées à l'intérieur de la rotule 20 creuse. Il est ainsi possible de diriger les axes d'émission 4 et de réception 5 dans une direction déterminée de l'espace, en particulier dans les directions dans lesquelles on cherche à détecter un nageur, à la manière d'un oeil pivotant dans l'orbite crânienne. Le diamètre D du transducteur électroacoustique d'émission est choisi de manière à faciliter l'installation dans l'épaisseur des parois 10, 11 de la piscine 12. Dans le cas de la variante de réalisation décrite, le diamètre D est de l'ordre de 10 centimètres .We will now describe an alternative embodiment of the electromechanical assembly in which all or part of the sonar 1 is mounted. This electromechanical assembly is composed of a box 9 fixed to the wall or to the bottom of the swimming pool 12, a transmitting antenna 2, a receiving antenna 3. In the case of the alternative embodiment shown in the figure 1, the housing 9 is produced in the form of a hollow swivel ball joint 20, movably mounted in a housing 90 arranged in the wall 10 or at the bottom 11 of the swimming pool 12. This ball joint 20 is actuated by means of orientation 14 driven by a motor 114. In the case of this alternative embodiment, the transmitting antenna 2 and the receiving antenna 3 are mounted inside the hollow ball joint. It is thus possible to direct the emission 4 and reception 5 axes in a determined direction of space, in particular in the directions in which it is sought to detect a swimmer, in the manner of an eye pivoting in the cranial orbit. The diameter D of the electroacoustic emission transducer is chosen so as to facilitate installation in the thickness of the walls 10, 11 of the swimming pool 12. In the case of the variant embodiment described, the diameter D is of the order of 10 centimeters.
Dans le cas d'une autre variante de réalisation, non représentée, l'antenne d'émission 2 et l'antenne de réception 3 sont montées sur des supports orientables 13 eux-mêmes montés de manière mobile à 1 ' intérieur du boîtier 9. De même que dans le cas de la précédente variante de réalisation, ces supports orientables sont actionnés par des moyens d'orientation 14 mus par un moteur 114. Dans le cas de cette variante de réalisation, le boîtier 9 est fixé à l'intérieur d'un logement 90 aménagé dans le mur 10 ou au fond 11 de la piscine 12.In the case of another alternative embodiment, not shown, the transmitting antenna 2 and the receiving antenna 3 are mounted on orientable supports 13 which are themselves movably mounted inside the housing 9. As in the case of the previous embodiment, these orientable supports are actuated by orientation means 14 driven by a motor 114. In the case of this embodiment, the housing 9 is fixed inside '' a housing 90 arranged in the wall 10 or at the bottom 11 of the swimming pool 12.
Avantageusement, dans le cas de ces variantes de réalisation, les moyens d'amplification 7 et de transmission 8, ainsi que les moyens d'orientation 14 et le moteur 114 sont contenus dans le boîtier 9 ou la rotule 20.Advantageously, in the case of these alternative embodiments, the amplification means 7 and transmission 8, as well as the orientation means 14 and the motor 114 are contained in the housing 9 or the ball joint 20.
Dans le cas de ces . variantes de réalisation, les antennes d'émission 2 et de réception 3 peuvent être orientées de manière à balayer automatiquement la zone submergée de la piscine 12. Il est ainsi possible de réaliser avec un nombre limité de sonars 1 une image tomographique de tout ou partie de ladite zone submergée, de même nature que celle précédemment décrite et- réalisée au moyen d'une pluralité de sonars 1 disposés en différents endroits de la piscine 12. In the case of these. variant embodiments, the transmitting 2 and receiving 3 antennas can be oriented so as to automatically scan the submerged area of the swimming pool 12. It is thus possible to produce a tomographic image of all or part with a limited number of sonars 1 of said submerged zone, of the same kind as that previously described and produced by means of a plurality of sonars 1 placed in different locations of the swimming pool 12.

Claims

REVENDICATIONS
1. Système d'alarme pour aider à la prévention des noyades ; ledit système comprenant au moins un sonar (1) , chaque sonar (1) comportant :1. Alarm system to help prevent drowning; said system comprising at least one sonar (1), each sonar (1) comprising:
- au moins une antenne d'émission (2) et une antenne de réception (3) ayant des axes d'émission (4) et de réception- at least one transmit antenna (2) and one receive antenna (3) having transmit (4) and receive axes
(5) ; lesdites antennes d'émission (2) et de réception (3) pouvant notamment se présenter sous la forme d'une seule antenne ; ledit sonar (1) étant du type sonar paramétrique à forte directivité spatiale selon lesdits axes d'émission (4) et/ou de réception (5) ; l'ouverture angulaire des lobes d'émission (17) et/ou de réception (18) desdites antennes d'émission (2) et/ou de réception (3) étant de l'ordre du degré ou inférieure au degré ; lesdites antennes d'émission (2) et de réception (3) étant destinées à délivrer des signaux acoustiques et à recevoir des signaux électriques ou inversement ; ledit système comprenant en outre :(5); said transmitting (2) and receiving (3) antennas can in particular be in the form of a single antenna; said sonar (1) being of the parametric sonar type with high spatial directivity along said transmission (4) and / or reception (5) axes; the angular opening of the transmitting (17) and / or receiving (18) lobes of said transmitting (2) and / or receiving (3) antennas being of the order of a degree or less than a degree; said transmitting (2) and receiving (3) antennas being intended to deliver acoustic signals and to receive electrical signals or vice versa; said system further comprising:
- un calculateur de traitement (6) , ledit sonar (1) comportant en outre :- a processing computer (6), said sonar (1) further comprising:
- des moyens d'amplification (7) et des moyens de transmission (8) pour amplifier et transmettre, vers ledit calculateur de traitement (6) , lesdits signaux électriques provenant de ladite antenne de réception (3) , et/ou- amplification means (7) and transmission means (8) for amplifying and transmitting, to said processing computer (6), said electrical signals coming from said reception antenna (3), and / or
- des moyens d'amplification (7) et des moyens de transmission (8) pour amplifier et transmettre, vers ladite antenne d'émission (2), les' signaux électriques provenant dudit calculateur de traitement (6) .- amplification means (7) and transmission means (8) for amplifying and transmitting, to said transmitting antenna (2), the ' electrical signals coming from said processing computer (6).
2. Système selon la revendication 1 ; ledit système comprenant en outre des boîtiers (9) ; chaque boîtier (9) étant fixé au mur (10) ou au fond (11) de la piscine (12) ; lesdites antennes d'émission (2) et de réception (3) étant montées, à l'intérieur desdits boîtiers (9), sur des supports orientables (13), notamment à l'intérieur des boîtiers (9) se présentant sous la forme de rotules (20) ; chaque boîtier (9). comportant en outre des moyens d'orientation (14) pour actionner lesdits supports orientables (13) et pour diriger lesdits axes d'émission (4) et/ou de réception (5) desdites antennes d'émission (2) et/ou de réception (3) dans une direction particulière de l'espace. 2. System according to claim 1; said system further comprising housings (9); each box (9) being fixed to the wall (10) or to the bottom (11) of the swimming pool (12); said transmitting (2) and receiving (3) antennas being mounted, inside said boxes (9), on orientable supports (13), in particular inside the boxes (9) in the form ball joints (20); each housing (9) . further comprising orientation means (14) for actuating said means orientable supports (13) and for directing said transmission (4) and / or reception (5) axes of said transmission (2) and / or reception (3) antennas in a particular direction of space.
3. Système selon l'une quelconque des revendications 1 ou 2 ; ledit système comprenant des moyens de modulation (15) pour moduler l'énergie acoustique émise par ledit sonar (1) ; lesdits moyens de modulation (15) permettant de moduler par un signal basse fréquence audible l'énergie acoustique émise par ledit sonar (1) ; ledit signal basse fréquence portant notamment un message vocal à destination d'un nageur (16) .3. System according to any one of claims 1 or 2; said system comprising modulation means (15) for modulating the acoustic energy emitted by said sonar (1); said modulation means (15) making it possible to modulate, by an audible low frequency signal, the acoustic energy emitted by said sonar (1); said low frequency signal carrying in particular a voice message intended for a swimmer (16).
4. Système selon l'une quelconque des revendications 2 ou 3 ; ledit système étant tel que lesdits lobes d'émission (17) et/ou de réception (18) sont coaxiaux et dirigés selon l'axe d'émission (4) et de réception (5) desdites antennes d'émission4. System according to any one of claims 2 or 3; said system being such that said transmit (17) and / or receive (18) lobes are coaxial and directed along the axis of emission (4) and reception (5) of said transmit antennas
(2) et de réception (3) ,(2) and reception (3),
(de sorte que lesdits moyens d'orientation (14 ) permettent d'orienter simultanément l 'axe d'émission (4) et l 'axe de réception (5) desdites antennes d'émission (2) et de réception (3) ) .(so that said orientation means (14) make it possible to simultaneously orient the transmission axis (4) and the reception axis (5) of said transmission (2) and reception (3) antennas) .
5. Système selon l'une quelconque des revendications 1 à 4 ; ledit système étant tel que lesdites antennes de réception5. System according to any one of claims 1 to 4; said system being such that said receiving antennas
(3) sont connectées auxdits moyens d'amplification (7) ; lesdits moyens d'amplification (7) étant situés à proximité desdites antennes de réception (3) ,(3) are connected to said amplification means (7); said amplification means (7) being located near said reception antennas (3),
(de sorte que le signal amplifié délivré audit calculateur de traitement (6) est de meilleure qualité) .(so that the amplified signal delivered to said processing computer (6) is of better quality).
6. Système selon l'une quelconque des revendications 1 à 5 ; ledit calculateur de traitement (6) activant des moyens d'alerte (19) .6. System according to any one of claims 1 to 5; said processing computer (6) activating alert means (19).
7. Système selon l'une quelconque des revendications 1 à 6 ; ledit calculateur de traitement (6) permettant d'estimer la quantité d'air contenue dans les poumons d'un nageur (16) en comparant lesdits signaux électriques reçus à des signaux préalablement mesurés.. 7. System according to any one of claims 1 to 6; said processing calculator (6) making it possible to estimate the amount of air contained in the lungs of a swimmer (16) by comparing said electrical signals received with previously measured signals.
8. Boîtier (9) destiné à aider à la prévention des noyades ; ledit boîtier (9) comportant au moins une antenne d'é¬ mission (2) et une antenne de réception (3) d'un sonar (1) ; lesdites antennes d'émission (2) et de réception (3) ayant des axes d'émission (4) et de réception (5) et pouvant notamment se présenter sous la forme d'une seule antenne ; ledit sonar (1) étant du type sonar (1) paramétrique à forte directivité spatiale selon lesdits axes d'émission (4) et/ou de réception (5) ; l'ouverture angulaire des lobes d'émission (17) et/ou de réception (18) desdites antennes d'émission (2) et/ou de réception (3) étant de l'ordre du degré ou inférieure au degré ; lesdites antennes d'émission (2) et de réception (3) étant destinées à délivrer des signaux acoustiques et à recevoir des signaux électriques ou inversement ; lesdits signaux électriques étant destinés à être transmis à un calculateur de traitement (6), via des moyens d'amplification (7) et des moyens de transmission (8) ; lesdits boîtiers étant destinés à être fixés au mur (10) ou au fond (11) de la piscine (12) ; ledit boîtier (9) comprenant de manière optionnelle : o des supports orientables (13) sur lesquels sont montées lesdites antennes d'émission et de réception (18), et/ou se présentant sous la forme d'une rotule (20) creuse à l'intérieur de laquelle sont montées lesdites antennes d'émission (2) et de réception (3), et/ou o des moyens d'orientation (14) pour actionner lesdits supports orientables (13) ou ladite rotule (20) creuse et pour diriger lesdits axes d'émission (4) ou de réception (5) desdites antennes d'émission (2) et de réception. (3) dans une direction particulière de l'espace, et/ou o des moyens de modulation (15) pour moduler l'énergie acoustique émise par ledit sonar (1) ; lesdits moyens de modulation (15) permettant de moduler par un signal basse fréquence audible l'énergie acoustique émise par ledit sonar (1) ; ledit signal basse fréquence portant notamment un message vocal à destination d'un nageur (16) , et/ou o des antennes d'émission (2) et de réception (3) telles que lesdits lobes d'émission (17) et/ou de réception (18) sont coaxiaux et dirigés selon l'axe d'émission (4) et de réception (5) desdites antennes d'émission (2) et de réception (3), et/ou o des moyens d'amplification (7) et/ou des moyens de transmission (8) desdits signaux électriques vers ledit calculateur de traitement (6) .8. Housing (9) to help prevent drowning; said housing (9) having at least one antenna é ¬ assignment (2) and a receiving antenna (3) of a sonar (1); said transmit (2) and receive (3) antennas having transmit (4) and receive (5) axes and which can in particular be in the form of a single antenna; said sonar (1) being of the parametric sonar type (1) with high spatial directivity along said transmission (4) and / or reception (5) axes; the angular opening of the transmitting (17) and / or receiving (18) lobes of said transmitting (2) and / or receiving (3) antennas being of the order of a degree or less than a degree; said transmitting (2) and receiving (3) antennas being intended to deliver acoustic signals and to receive electrical signals or vice versa; said electrical signals being intended to be transmitted to a processing computer (6), via amplification means (7) and transmission means (8); said boxes being intended to be fixed to the wall (10) or to the bottom (11) of the swimming pool (12); said housing (9) optionally comprising: o orientable supports (13) on which said transmitting and receiving antennas (18) are mounted, and / or being in the form of a hollow ball joint (20) with inside which are mounted said transmitting (2) and receiving (3) antennas, and / or o orientation means (14) for actuating said orientable supports (13) or said hollow ball joint (20) and to direct said transmission (4) or reception (5) axes of said transmission (2) and reception antennas . (3) in a particular direction of space, and / or o modulation means (15) for modulating the acoustic energy emitted by said sonar (1); said modulation means (15) making it possible to modulate, by an audible low frequency signal, the acoustic energy emitted by said sonar (1); said low frequency signal carrying in particular a voice message intended for a swimmer (16), and / or o transmit (2) and receive (3) antennas such that said transmit (17) and / or receive (18) lobes are coaxial and directed along the transmit (4) and receive axis (5) of said transmitting (2) and receiving (3) antennas, and / or o amplification means (7) and / or transmission means (8) of said electrical signals to said processing computer (6 ).
9. Procédé pour aider à la prévention des noyades ; ledit procédé comprenant l'étape de détecter un nageur (16) et son positionnement en mettant en oeuvre un sonar (1) paramétrique, à forte directivité spatiale, ayant une ouverture angulaire des lobes d'émission (17) et/ou de réception (18) de l'ordre du degré ou inférieure au degré ; ledit procédé comprenant en option ;9. Process to help prevent drowning; said method comprising the step of detecting a swimmer (16) and its positioning by using a parametric sonar (1), with high spatial directivity, having an angular opening of the emission (17) and / or reception lobes ( 18) of the order of a degree or less than a degree; said method optionally comprising;
- l'étape d'estimer le degré de mobilité du nageur (16) , et/ou- the step of estimating the degree of mobility of the swimmer (16), and / or
- l'étape d'estimer la quantité d'air restant dans les poumons dudit nageur (16) , et/ou - l'étape d'émettre vers ledit nageur (16) des signaux audibles au moyen dudit sonar (1) paramétrique.- the step of estimating the quantity of air remaining in the lungs of said swimmer (16), and / or - the step of transmitting towards said swimmer (16) audible signals by means of said parametric sonar (1).
10. Utilisation d'un sonar (1) paramétrique, à forte directivité spatiale, ayant une ouverture angulaire des lobes d'émission (17) et/ou de réception (18) de l'ordre du degré ou inférieure au degré, dans un système de prévention des noyades. 10. Use of a parametric sonar (1), with strong spatial directivity, having an angular opening of the emission (17) and / or reception (18) lobes of the order of the degree or less than the degree, in a drowning prevention system.
EP01928041A 2000-04-26 2001-04-24 Warning method, system and device based on transmission of acoustic signals Withdrawn EP1290472A1 (en)

Applications Claiming Priority (3)

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FR0005301 2000-04-26
FR0005301A FR2808364B3 (en) 2000-04-26 2000-04-26 ALARM DEVICE BASED ON AN ACOUSTIC SYSTEM
PCT/FR2001/001247 WO2001081947A1 (en) 2000-04-26 2001-04-24 Warning method, system and device based on transmission of acoustic signals

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EP (1) EP1290472A1 (en)
AU (1) AU2001254910A1 (en)
CA (1) CA2407131A1 (en)
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GB2416898A (en) * 2004-08-05 2006-02-08 Vincent Robert Brewer Subsurface wave sensing pool alarm
FR3001566A1 (en) * 2013-01-31 2014-08-01 Datasharing Detection device for detection of living body i.e. young child in swimming pool, has detection unit detecting living body as function of phase difference between received periodic signal modulated by living body and transmitted signal

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FR2808364B3 (en) 2002-07-05
US20030147307A1 (en) 2003-08-07

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