WO2003009499A2 - Dispositif d'ecoute /anti-ecoute clandestine - Google Patents

Dispositif d'ecoute /anti-ecoute clandestine Download PDF

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Publication number
WO2003009499A2
WO2003009499A2 PCT/GB2002/003249 GB0203249W WO03009499A2 WO 2003009499 A2 WO2003009499 A2 WO 2003009499A2 GB 0203249 W GB0203249 W GB 0203249W WO 03009499 A2 WO03009499 A2 WO 03009499A2
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WO
WIPO (PCT)
Prior art keywords
transducer
modes
resonant element
distribution
resonant
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PCT/GB2002/003249
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English (en)
Other versions
WO2003009499A3 (fr
Inventor
Martin Christopher Cassey
Graham Bank
Neil Owen
Neil Harris
Martin Colloms
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New Transducers Limited
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Publication date
Application filed by New Transducers Limited filed Critical New Transducers Limited
Priority to AU2002313529A priority Critical patent/AU2002313529A1/en
Publication of WO2003009499A2 publication Critical patent/WO2003009499A2/fr
Publication of WO2003009499A3 publication Critical patent/WO2003009499A3/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B11/00—Transmission systems employing sonic, ultrasonic or infrasonic waves

Definitions

  • TECHNICAL FIELD This invention relates to a method for adapting a room to provide a listening or anti-eavesdropping device.
  • a method of transmitting information from a conversation in a room to a remote listener comprising selecting a structure in the room which is capable of supporting vibration, selecting an electromechanical force transducer which has an intended operative frequency range and comprises a resonant element having a frequency- distribution of modes in the operative frequency range, mounting the transducer to the radiator using coupling means whereby the transducer excites vibration in the radiator, positioning a sensor to detect vibration in the radiator, determining information from the detected vibration and transmitting said information to a remote listener.
  • the structure may be a window or wall-panel of the room.
  • the method may further comprise calculating the mechanical impedance of the structure and modifying the parameters of the transducer to match the mechanical impedance of the transducer to that of the structure . By matching the mechanical impedance, maximum mechanical coupling efficiency may be achieved but even a mismatch may give useful transfer of mechanical power.
  • the transducer preferably excites vibration at ultrasonic frequencies in the structure and the sensor may be an ultrasonic microphone.
  • the transducer of the present invention is preferably broad band and may thus transmit a multi-frequency signal. Hence a large number of channels may be simultaneously transmitted.
  • a listening system made in accordance with the method above.
  • the listening system comprises a structure in a room, the structure being capable of supporting vibration, a transducer mounted via coupling means to the structure to excite vibration in the structure, the transducer having an intended operative frequency range and comprising a resonant element having a frequency distribution of modes in the operative frequency range, a sensor for detecting vibration in the radiator, means for determining information from the detected vibration and means for transmitting the information to a remote listener.
  • listening devices may be devised which comprise sensors, e.g. laser beams, which detect such vibration whereby a third party may listen to the conversation.
  • an anti-eavesdropping system to counteract such a listening device.
  • the anti-eavesdropping system is the reverse of the method and device according to the first and second aspects of the invention.
  • the anti-eavesdropping system comprises a transducer mounted via coupling means to a room structure which is capable of supporting vibration, the transducer having an intended operative frequency range and comprising a resonant element having a frequency distribution of modes in the operative frequency range, characterised in that a broadband noise signal is fed into the transducer to excite vibration in the structure whereby vibration produced by alternative sources is masked.
  • the resonant element may be active e.g. may be a piezoelectric transducer and may be in the form of a strip of piezoelectric material.
  • the resonant element may be passive and the transducer may further comprise an active transducer, e.g. an inertial or grounded vibration transducer, actuator or exciter, e.g. moving coil transducer.
  • the active transducer may be a bender or torsional transducer (e.g. of the type taught in WOOO/13464) .
  • the transducer may comprise combination of passive and active elements to form a hybrid transducer.
  • transducer, exciter or actuator mechanisms have been developed to apply a force to a structure, e.g. an acoustic radiator of a loudspeaker.
  • a structure e.g. an acoustic radiator of a loudspeaker.
  • transducer mechanisms for example moving coil, moving magnet, piezoelectric or magnetostrictive types.
  • electrodynamic speakers using coil and magnet type transducers lose 99% of their input energy to heat whereas a piezoelectric transducer may lose as little as 1%.
  • piezoelectric transducers are popular because of their high efficiency.
  • piezoelectric transducers There are several problems with piezoelectric transducers, for example, they are inherently very stiff, for example comparable to brass foil, and are thus difficult to match to an acoustic radiator, especially to the air. Raising the stiffness of the transducer moves the fundamental resonant mode to a higher frequency. Thus such piezoelectric transducers may be considered to have two operating ranges.
  • the first operating range is below the fundamental resonance of the transducer. This is the "stiffness controlled" range where velocity rises with frequency and the output response usually needs equalisation. This leads to a loss in available efficiency.
  • the second range is the resonance range beyond the stiffness range, which is generally avoided because the resonances are rather fierce.
  • piezoelectric transducers are generally used only used in the frequency range below or at the fundamental resonance of the transducers . Where piezoelectric transducers are used above the fundamental resonance frequency it is necessary to apply damping to suppress resonance peaks .
  • piezoelectric transducers comprising other "smart" materials, i.e. magnetostrictive, electrostrictive, and electret type materials.
  • Various piezoelectric transducers are also known, for example as described in EP 0993 231A of Shinsei Corporation, EP 0881 856A of Shinsei Corporation, US 4,593,160 OF Murata Manufacturing Co. Limited, US 4,401,857 of Sanyo Electric Co Limited, US 4,481,663 of Altec Corporation and UK patent application GB2,166,022A of Sawafuj i .
  • the transducer used in the present invention may be considered to be an intendedly modal transducer.
  • the coupling means may be attached to the resonant element at a position which is beneficial for coupling modal activity of the resonant element to the interface.
  • the parameters, e.g. aspect ratio, bending stiffness, thickness and geometry, of the resonant element may be selected to enhance the distribution of modes in the resonant element in the operative frequency range.
  • the bending stiffness and thickness of the resonant element may be selected to be isotropic or anisotropic.
  • the variation of bending stiffness and/or thickness may be selected to enhance the distribution of modes in the resonant element.
  • Analysis e.g. computer simulation using FEA or modelling, may be used to select the parameters.
  • the parameters of the transducer may be selected to provide a low cost, thin, lightweight and low power transducer. Thus, the transducer may be continuously deployed without consuming large quantities of power.
  • the distribution may be enhanced by ensuring a first mode of the active element is near to the lowest operating frequency of interest.
  • the distribution may also be enhanced by ensuring a satisfactory, e.g. high, density of modes in the operative frequency range.
  • the density of modes is preferably sufficient for the active element to provide an effective mean average force which is substantially constant with frequency. Good energy transfer may provide beneficial smoothing of modal resonances.
  • the distribution of modes may be enhanced by distributing the resonant bending wave modes substantially evenly in frequency, i.e. to smooth peaks in the frequency response caused by "bunching" or clustering of the modes.
  • Such a transducer may thus be known as a distributed mode transducer or DMT.
  • the transducer may comprise a plurality of resonant elements each having a distribution of modes, the modes of the resonant elements being arranged to interleave in the operative frequency range and thus enhance the distribution of modes in the transducer as a whole device .
  • the resonant elements may have different fundamental frequencies and thus, the parameters, e.g. loading, geometry or bending stiffness of the resonant elements may be different.
  • the resonant elements may be coupled together by connecting means in any convenient way, e.g. on generally stiff stubs, between the elements.
  • the resonant elements are preferably coupled at coupling points which enhance the modality of the transducer and/or enhance the coupling at the site to which the force is to be applied. Parameters of the connecting means may be selected to enhance the modal distribution in the resonant element.
  • the resonant elements may be arranged in a stack.
  • the coupling points may be axially aligned.
  • the resonant element may be plate-like or may be curved out of planar.
  • a plate-like resonant element may be formed with slots or discontinuities to form a multi- resonant system.
  • the resonant element may be in the shape of a beam, trapezoidal, hyperelliptical or may be generally disc shaped.
  • the resonant element may be rectangular and may be curved out of the plane of the rectangle about an axis along the short axis of symmetry.
  • the resonant element may be modal along two substantially normal axes, each axis having an associated fundamental frequency.
  • the ratio of the two fundamental frequencies may be adjusted for best modal distribution, e.g. 9:7 (-1.286:1) .
  • the arrangement of such modal transducer may be any of: a flat piezoelectric disc; a combination of at least two or preferably at least three flat piezoelectric discs; two coincident piezoelectric beams; a combination of multiple coincident piezoelectric beams; a curved piezoelectric plate; a combination of multiple curved piezoelectric plates or two coincident curved piezoelectric beams.
  • the interleaving of the distribution of the modes in each resonant element may be enhanced by optimising the frequency ratio of the resonant elements, namely the ratio of the frequencies of each fundamental resonance of each resonant element.
  • the parameter of each resonant element relative to one another may be altered to enhance the overall modal distribution of the transducer.
  • the two beams may have a frequency ratio (i.e. ratio of fundamental frequency) of 1.27:1.
  • the frequency ratio may be 1.315:1.147:1.
  • the frequency ratio may be 1.1 +/- 0.02 to 1 to optimise high order modal density or may be 3.2 to 1 to optimise low order modal density.
  • the frequency ratio may be 3.03:1.63:1 or may be 8.19:3.20:1.
  • the parameters of the coupling means may be selected to enhance the distribution of modes in the resonant element in the operative frequency range.
  • the coupling means may be vestigial, e.g. a controlled layer of adhesive.
  • the coupling means may be positioned asymmetrically with respect to the panel so that the transducer is coupled asymmetrically. The asymmetry may be achieved in several ways, for example by adjusting the position or orientation of the transducer with respect to axes of symmetry in the panel or the transducer.
  • the coupling means may form a line of attachment.
  • the coupling means may form a point or small local area of attachment where the area of attachment is small in relation to the size of the resonant element.
  • the coupling means may be in the form of a stub and have a small diameter, e.g. 3 to 4 mm.
  • the coupling means may be low mass.
  • the coupling means may comprise more than one coupling point and may comprise a combination of points and/or lines of attachment. For example, two points or small local areas of attachment may be used, one positioned near centre and one positioned at the edge of the active element. This may be useful for plate-like transducers which are generally stiff and have high natural resonance frequencies .
  • a single coupling point may be provided. This may provide the benefit, in the case of a multi-resonant element array, that the output of all the resonant elements is summed through the single coupling means so that it is not necessary for the output to be summed by the load.
  • the coupling means may be chosen to be located at an anti-node on the resonant element and may be chosen to deliver a constant average force with frequency.
  • the coupling means may be positioned away from the centre of the resonant element .
  • the position and/or the orientation of the line of attachment may be chosen to optimise the modal density of the resonant element.
  • the line of attachment is preferably not coincident with a line of symmetry of the resonant element.
  • the line of attachment may be offset from the short axis of symmetry (or centre line) of the resonant element.
  • the line of attachment may have an orientation which is not parallel to a symmetry axis of the panel.
  • the shape of the resonant element may be selected to provide an off-centre line of attachment which is generally at the centre of mass of the resonant element.
  • One advantage of this embodiment is that the transducer is attached at its centre of mass and thus there is no inertial imbalance. This may be achieved by an asymmetric shaped resonant element which may be in the shape of a trapezium or trapezoid.
  • the line of attachment may extend across the width of the resonant element.
  • the area of the resonant element may be small relative to that of the acoustic radiator.
  • the acoustic radiator may be in the form of a panel.
  • the panel may be flat and may be lightweight.
  • the material of the acoustic radiator may be anisotropic or isotropic.
  • the properties of the acoustic radiator may be chosen to distribute the resonant bending wave modes substantially evenly in frequency, i.e. to smooth peaks in the frequency response caused by "bunching" or clustering of the modes.
  • the properties of the acoustic radiator may be chosen to distribute the lower frequency resonant bending wave modes substantially evenly in frequency.
  • the lower frequency resonant bending wave modes are preferably the ten to twenty lowest frequency resonant bending wave modes of the acoustic radiator.
  • the transducer location may be chosen to couple substantially evenly to the resonant bending wave modes in the acoustic radiator, in particular to lower frequency resonant bending wave modes.
  • the transducer may be mounted at a location where the number of vibrationally active resonance anti-nodes in the acoustic radiator is relatively high and conversely the number of resonance nodes is relatively low. Any such location may be used, but the most convenient locations are the near-central locations between 38% to 62% along each of the length and width axes of the acoustic radiator, but off-centre. Specific or preferential locations are at 3/7,4/9 or 5/13 of the distance along the axes; a different ratio for the length axis and the width axis is preferred.
  • the force may be taken from the centre of the beam, and may be matched to the mode shape in the acoustic radiator to which it is attached. In this way, the action and reaction may co-operate to give a constant output with frequency.
  • the resonant element By connecting the resonant element to the acoustic radiator at an anti-node of the resonant element, the first resonance of the resonant element may appear to be a low impedance. In this way, the acoustic radiator should not amplify the resonance of the resonant element.
  • the invention may be extended to ultrasonic BAT personnel location devices, ultrasonic motion sensors or single or multi-function security sensor, e.g. by exciting everyday objects to act as transmitters. Operation over a range greater than the range defined by a single dominant, natural resonance of the transducer may be achieved.
  • the lowest frequency in the operative frequency range is preferably above a predetermined lower limit which is about the fundamental resonance of the transducer.
  • Figure 8 is a plan view of an alternative modal transducer according to in the present invention
  • Figure 9A is a schematic plan view of a parameterised model of a transducer according to the present invention.
  • Figure 9B is a section perpendicular to the line of attachment of the transducer of Figure 9A;
  • Figure 10A is a schematic plan view of a parameterised model of a transducer according to the present invention
  • Figure 10B is a section perpendicular to the line of attachment of the transducer of Figure 10A;
  • Figure 11 is a front view of a window glazing unit which may be adapted to embody both embodiments of the present invention.
  • Figure 12 is a partial sectional view of the window glazing unit of Figure 11 showing the anti-eavesdropping embodiment
  • Figure 13a is a partial sectional view of the window glazing unit of Figure 11 showing a first listening device
  • Figure 13b is a partial sectional view of the window glazing unit of Figure 11 showing a second listening device .
  • Figures 1 to 10B show a variety of transducers which are designed to operate over a broad bandwidth and are designed to be mounted to a panel or other load device which is a found device in a room, e.g. a window or wall panel .
  • FIG. 1 shows a transducer (42) which comprises a first piezoelectric beam (43) on the back of which is mounted a second piezoelectric beam (51) by connecting means in the form of a stub (48) located at the centre of both beams.
  • Each beam is a bi-morph.
  • the first beam (43) comprises two layers (44,46) of piezoelectric material and the second beam (51) comprises two layers (50,52).
  • the poling directions of each layer of piezoelectric material are shown by arrows (49) .
  • Each layer (44, 50) has an opposite poling direction to the other layer (46, 52) in the bi-morph.
  • the bi-morph may also comprise a central conducting vane which allows a parallel electrical connection as well as adding a strengthening component to the ceramic piezoelectric layers.
  • Each layer of each beam (44, 46) may be made of the same/different piezoelectric material. Each layer is generally of a different length.
  • the first piezoelectric beam (43) is mounted on a panel (54) by coupling means in the form of a stub (56) located at the centre of the first beam.
  • a stub located at the centre of the first beam.
  • the second beam may be chosen by using the ratio of the fundamental resonance of the two beams. If the materials and thicknesses are identical, then the ratio of frequencies is just the square of the ratio of lengths. If the higher fO (fundamental frequency) is simply placed half way between fO and fl of the other, larger beam, f3 of the smaller beam and f4 of the lower beam coincide.
  • the method of combining active elements may be extended to using piezoelectric discs .
  • the ratio of sizes of the two discs depends upon how many modes are taken into consideration. For high order modal density, a ratio of fundamental frequencies of about 1.1 +/- 0.02 to 1 may give good results. For low order modal density (i.e. the first few or first five modes), a ratio of fundamental frequencies of about 3.2:1 is good. The first gap comes between the second and third modes of the larger disc.
  • ⁇ ⁇ are (1.63, 3.03) and (3.20, 8.19). These optima are quite shallow, meaning that variations of 10%, or even 20%, in the parameter values are acceptable.
  • An alternative approach for determining the different discs to be combined is to consider the cost as a function of the ratio of the radii of the three discs.
  • the cost functions may be RSCD (ratio of sum of central differences) , SRCD (sum of the ratio of central differences) and SCR (sum of central ratios) .
  • RSCD ratio of sum of central differences
  • SRCD sum of the ratio of central differences
  • SCR sum of central ratios
  • passive elements may be incorporated into the transducer to improve its overall modality. The active and passive elements may be arranged in a cascade. Figure 2 shows a multiple disc transducer
  • (70) comprising two active piezoelectric elements (72) stacked with two passive resonant elements (74), e.g. thin metal plates so that the modes of the active and passive elements are interleaved.
  • the elements are connected by connecting means in the form of stubs (78) located at the centre of each active and passive element .
  • the elements are arranged concentrically. Each element has different dimensions with the smallest and largest discs located at the top and bottom of the stack, respectively.
  • the transducer (70) is mounted on a load device (76), e.g. a panel, by coupling means in the form of a stub (78) located at the centre of the first passive device which is the largest disc.
  • small masses (104) may be mounted at the end of the piezoelectric transducer (106) having coupling means (105).
  • the transducer In Figure 4, the transducer
  • (114) is an inertial electrodynamic moving coil exciter, e.g. as described in WO97/09842, having a voice coil forming an active element (115) and a passive resonant element in the form of a modal plate (118) .
  • the active element (115) is mounted on the modal plate (118) and off- centre of the modal plate.
  • the modal plate (118) is mounted on the panel (116) by a coupler (120) .
  • the coupler is aligned with the axis (117) of the active element but not with the axis (Z) normal to the plane of the panel (116) .
  • the active element is connected to an electrical signal input via electrical wires (122) .
  • the modal plate (118) is perforate to reduce the acoustic radiation therefrom and the active element is located off-centre of the modal plate (118) , for example, at the optimum mounting position, i.e. (3/7, 4/9).
  • FIG. 5 shows a transducer (124) comprising an active piezoelectric resonant element which is mounted by coupling means (126) in the form of a stub to a panel (128) .
  • Both the transducer (124) and panel (128) have ratios of width to length of 1:1.13.
  • the coupling means (126) is not aligned with any axes (130, Z) of the transducer or the panel. Furthermore, the placement of the coupling means is located at the optimum position, i.e. off-centre with respect to both the transducer (124) and the panel (128) .
  • FIG. 6 shows a transducer (132) in the form of active piezoelectric resonant element in the form of a beam.
  • the transducer (132) is coupled to a panel (134) by two coupling means (136) in the form of stubs.
  • One stub is located towards an end (138) of the beam and the other stub is located towards the centre of the beam.
  • FIG. 7 shows a transducer (140) comprising two active resonant elements (142,143) coupled by connecting means (144) and an enclosure (148) which surrounds the connecting means (144) and the resonant elements (142) .
  • the transducer is thus made shock and impact resistant.
  • the enclosure is made of a low mechanical impedance rubber or comparable polymer so as not to impede the transducer operation. If the polymer is water resistant, the transducer (140) may be made waterproof.
  • the upper resonant element (142) is larger than the lower resonant element (143) which is coupled to a panel
  • the power couplings (150) for each active element extend from the enclosure to allow good audio attachment to a load device (not shown) .
  • FIG 8 shows a transducer (160) in the form of a plate-like active resonant element.
  • the resonant element is formed with slots (162) which define fingers (164) and thus form a multi-resonant system.
  • the resonant element is mounted on a panel (168) by a coupling means in the form of a stub (166) .
  • the transducer (14) is rectangular with out-of-plane curvature and is a pre- stressed piezoelectric transducer of the type disclosed in US patent 5632841 (International patent application WO 96/31333) and produced by PAR Technologies Inc under the trade name NASDRIV.
  • the transducer (14) is an active resonant element .
  • the transducer has width (W) and length (L) and the position (x) of the attachment point (16) .
  • the curvature of the transducer (14) means that the coupling means (16) is in the form of a line of attachment.
  • the optimum suspension point may be modelled and is has the line of attachment at 43% to 44% along the length of the resonant element .
  • the cost function (or measure of "badness") is minimised at this value; this corresponds to an estimate for the attachment point at 4/9 ths of the length.
  • computer modelling showed this attachment point to be valid for a range of transducer widths.
  • a second suspension point at 33% to 34% along the length of the resonant element also appears suitable.
  • the optimum aspect ratio may be determined to be 1.06 +/- 0.01 to 1 since the cost function is minimised at this value.
  • the optimum angle of attachment ⁇ to the panel (12) may be determined using two "measures of badness” to find the optimum angle.
  • the standard deviation of the log (dB) magnitude of the response is a measure of "roughness”.
  • Such figures of merit/badness are discussed in International Application WO 99/41939, to the present applicants.
  • Figures 10A and 10B show an asymmetrically shaped transducer (18) in the form of a resonant element having a trapezium shaped cross-section.
  • the shape of a trapezium is controlled by two parameters, AR (aspect ratio) and TR (taper ratio) .
  • AR and TR determine a third parameter, ⁇ , such that some constraint is satisfied - for example, equal mass either side of the line.
  • a trapezoidal transducer is thus that the transducer may be mounted along a line of attachment which is at its centre of gravity/mass but is not a line of symmetry. Such a transducer would thus have the advantages of improved modal distribution, without being inertially unbalanced.
  • Figures 11, 12, 13a and 13b show a window-glazing unit, comprising a frame (100) and a glass window (101) , which may comprise a single or multiple glazed sheets.
  • the frame (100) extends around the periphery of the window and has a generally U-shaped cross-section defining a channel (103) .
  • the edges of the window (101) are held within the channel by a flexible mount.
  • An intendedly modal transducer (90) or distributed mode transducer as hereinbefore described and as described in WO 01/54450 and US 09/768,002 is mounted to a coupling means (68) in the form of a connecting stub which is connected to the window (101) .
  • the distributed mode transducer (90) comprises upper and lower bi-morph beams (84) and (86) connected by a connecting stub (88) .
  • the upper beam (84) is connected to the coupling means (68) which extends across the width of the beams.
  • the mechanical impedance of the transducer may be matched to that of the window for improved efficiency. Electrical connections to the transducer (90) are made by way of wires (92) .
  • a mask (102) may be fixed or printed onto the outside (or inside) surface of the window in order to conceal the transducer from an external observer.
  • the transducer may be used to drive bending wave vibrations into the window. The nature of the resulting bending waves is determined by the signal received by the transducer.
  • the laser detection system may comprise an emitting laser ( 96) and remote velocity sensor (94) , such as a laser interferometer.
  • a laser beam (93) is trained on the window from the laser (96) and the reflected beam (95) contains information regarding both sets of vibrations. This effectively swamps the laser detection system and thus, the apparatus acts as an anti- eavesdropping device .
  • a high frequency signal above the normal threshold of hearing, may be applied to the transducer. This will set up vibrations in the window which produce an inaudible output . Speech occurring in a room adjacent the window will set up low-level vibration in the window which will interfere with the vibrations from the transducer. Since the vibration applied by the transducer is known, either the vibration or the inaudible output may be measured to derive the nature of the vibrations set up by speech and hence listen to the speech. Accordingly, a listening device is formed.
  • the vibrations may be monitored using a vibration detection system which is similar to the laser detection system of Figure 12.
  • a vibration detection system which is similar to the laser detection system of Figure 12.
  • the inaudible output (97) from the window is detected by the microphone (99) .
  • the system detecting vibration or output is remote from the window.
  • a laser interferometer monitors the velocity of the window glass.
  • the laser interferometer comprises a remote velocity sensor (94) and a laser (96) .
  • a laser beam (93) is trained on the window from the laser
  • the laser beam may have a single carrier frequency which is carried to the remote system.
  • the laser beam may be modulated to simultaneously carry more than one signal time by multiplexing the reflected beam before modulating the signal transducer applied to the transducer.
  • the transducer used in the present invention may be seen as the reciprocal of a distributed mode panel, e.g. as described in WO97/09842, in that the transducer is designed to be a distributed mode object.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Abstract

L'invention concerne un procédé et un appareil de transmission d'informations d'une conversation ayant lieu dans une pièce vers un auditeur à distance. Le procédé consiste à sélectionner une structure (101) dans la pièce capable de supporter des vibrations et à sélectionner un transducteur de force électromécanique (90). Ledit transducteur présente une plage de fréquence d'activité souhaitée et comprend un élément résonant (84, 86) présentant une distribution de fréquence de modes dans la plage de fréquence d'activité. Le transducteur (90) est monté sur la structure (101) au moyen d'éléments de couplage (68) pour exciter une vibration dans la structure. Un capteur est positionnée afin de détecter des vibrations dans la structure (101). Le procédé consiste en outre à déterminer des informations à partir des vibrations détectées et à transmettre lesdites informations à un auditeur à distance. L'invention concerne également un système d'anti-écoute clandestine qui est l'inverse du procédé et de l'appareil présentés selon les premier et deuxième modes de réalisation de l'invention.
PCT/GB2002/003249 2001-07-20 2002-07-16 Dispositif d'ecoute /anti-ecoute clandestine WO2003009499A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002313529A AU2002313529A1 (en) 2001-07-20 2002-07-16 Listening/anti eavesdropping device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0117663.5 2001-07-20
GB0117663A GB0117663D0 (en) 2001-07-20 2001-07-20 Listening anti eavesdropping device

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WO2003009499A2 true WO2003009499A2 (fr) 2003-01-30
WO2003009499A3 WO2003009499A3 (fr) 2003-07-31

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GB (1) GB0117663D0 (fr)
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10328815A1 (de) * 2003-06-21 2005-01-05 Biotronik Meß- und Therapiegeräte GmbH & Co. Ingenieurbüro Berlin Beschichtungssystem für Implantate zur Erhöhung der Gewebsverträglichkeit
US7920822B2 (en) 2007-10-08 2011-04-05 Electronics And Telecommunications Research Institute Device for preventing eavesdropping through speaker

Citations (5)

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US4593160A (en) * 1984-03-09 1986-06-03 Murata Manufacturing Co., Ltd. Piezoelectric speaker
WO1997009842A2 (fr) * 1995-09-02 1997-03-13 New Transducers Limited Dispositif acoustique
WO2000035242A2 (fr) * 1998-12-09 2000-06-15 New Transducers Limited Haut-parleur
US6114684A (en) * 1998-05-19 2000-09-05 Mc Guire; James F. Laser listening device detector
WO2001054450A2 (fr) * 2000-01-24 2001-07-26 New Transducers Limited Transducteur

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Publication number Priority date Publication date Assignee Title
US4593160A (en) * 1984-03-09 1986-06-03 Murata Manufacturing Co., Ltd. Piezoelectric speaker
WO1997009842A2 (fr) * 1995-09-02 1997-03-13 New Transducers Limited Dispositif acoustique
US6114684A (en) * 1998-05-19 2000-09-05 Mc Guire; James F. Laser listening device detector
WO2000035242A2 (fr) * 1998-12-09 2000-06-15 New Transducers Limited Haut-parleur
WO2001054450A2 (fr) * 2000-01-24 2001-07-26 New Transducers Limited Transducteur

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10328815A1 (de) * 2003-06-21 2005-01-05 Biotronik Meß- und Therapiegeräte GmbH & Co. Ingenieurbüro Berlin Beschichtungssystem für Implantate zur Erhöhung der Gewebsverträglichkeit
US7920822B2 (en) 2007-10-08 2011-04-05 Electronics And Telecommunications Research Institute Device for preventing eavesdropping through speaker

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WO2003009499A3 (fr) 2003-07-31
AU2002313529A1 (en) 2003-03-03
GB0117663D0 (en) 2001-09-12

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