EP1317678A2 - Procede et appareil d'identification de la source d'un evenement impulsionnel ou explosif - Google Patents

Procede et appareil d'identification de la source d'un evenement impulsionnel ou explosif

Info

Publication number
EP1317678A2
EP1317678A2 EP01965444A EP01965444A EP1317678A2 EP 1317678 A2 EP1317678 A2 EP 1317678A2 EP 01965444 A EP01965444 A EP 01965444A EP 01965444 A EP01965444 A EP 01965444A EP 1317678 A2 EP1317678 A2 EP 1317678A2
Authority
EP
European Patent Office
Prior art keywords
explosive
hertz
impulsive
shock wave
acoustic
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Withdrawn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
EP01965444A
Other languages
German (de)
English (en)
Inventor
Roderick Charles Drew
Meng Li
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.)
Serco Ltd
Original Assignee
Serco Ltd
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 Serco Ltd filed Critical Serco Ltd
Publication of EP1317678A2 publication Critical patent/EP1317678A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F41—WEAPONS
    • F41H—ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL
    • F41H11/00—Defence installations; Defence devices
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves

Definitions

  • the present invention relates to a method and system for identifying the source of explosive or impulsive shock waves, such as artillery, from their acoustic signatures.
  • the present invention seeks to provide improved identification of the source of an explosive or impulsive event.
  • a method of identifying the source of an explosive or impulsive shock wave event including the steps of recording the event by converting acoustic sound pressure to an electrical signal using a sound pressure sensor, within a frequency range including at least part of the audio range, calculating at least sound energy level and the acoustic speed of the wavefront, and identifying therefrom the source of the explosive or impulsive event.
  • the frequency range is preferably from zero Hertz up to several thousand Hertz, more preferably from 0 Hertz to 10,000 Hertz and most preferably from 0 Hertz to around 20,000 Hertz.
  • the actual range of frequencies chosen for measurement depends upon factors such as the types of events sought to be identified and the accuracy of the identification required. Therefore, the preferred ranges given above could be changed, for example to start above zero Hertz, such as from a few tens of Hertz.
  • a system for identifying the source of an explosive or impulsive shock wave event including a sound pressure sensor operable to record the event by converting acoustic sound pressure to an electrical signal, the sound pressure sensor being operable within a frequency range including at least part of the audio range, and processing means operable to calculate at least sound energy level and the acoustic speed of the wavefront and to identify therefrom the source of the explosive or impulsive shock wave event.
  • the sound pressure sensor is preferably able to measure from a zero Hertz up to several thousand Hertz, more preferably from 0 Hertz to 10,000 Hertz and most preferably from 0 Hertz to around 20,000 Hertz.
  • the sound pressure sensor could measure a different range, for example starting above zero Hertz, such as from a few tens of Hertz.
  • the inventors have discovered that the energy content at higher audio frequency ranges contains important features about the shock wave event, even for signals that have suffered attenuation over distance.
  • a method of acquiring the signature of an explosive or impulsive shock wave event by delaying any data acquisition until triggering of a trigger device activated only by sound pressure from explosive or impulsive shock waves.
  • a system for acquiring the signature of an explosive or impulsive shock wave event including a trigger device activated only by sound pressure from an explosive or impulsive shock wave, data acquisition means, and control means operable to activate the acquisition means only upon triggering of the trigger device.
  • the trigger prevents the recording of unwanted sound waves, that is any sound waves not associated with an explosive or impulsive shock wave event. Continuous measurement results in time-consuming manual event selection prior to pre-processing. This makes it practically impossible to provide real-time or substantially real-time identification of the source of an explosive or impulsive shock wave event.
  • adoption of the trigger device enables the exclusive recording of events of interest, resulting in a very substantial reduction in the amount of data recorded and therefore the possibility of providing real-time or substantially real-time identification of the source of an explosive or impulsive shock wave event.
  • the trigger device comprises a chamber having a rigid or substantially rigid floating wall or panel within one wall, within which chamber there is provided a microphone.
  • the floating panel or wall is caused to vibrate by the sound impulse produced by an explosive or impulsive shock wave event impinging upon it.
  • the sound field in the chamber is a combination of the direct sound field from the source, transmitted through the entire surface of the chamber, the reverberant field and the emitted sound from vibration of the panel comprising a part of the surface of the enclosure.
  • both the directly transmitted sound and the sound emitted from the panel to the microphone will have an impulsive nature. This will greatly enhance the sound field, and only in this case will the microphone apply a sufficiently high voltage to initiate data acquisition.
  • the system will only commence data acquisition when triggered by an explosive wave.
  • a trigger operable to initiate data acquisition of an explosive or impulsive shock wave event, including a chamber comprising a rigid or substantially rigid floating panel or wall and a sound pressure sensor within the chamber.
  • the sound pressure sensor is preferably a microphone.
  • the present invention can be used to identify sources of explosive or impulsive shock waves, such as artillery, from their acoustic signatures.
  • the preferred embodiments incorporate both hardware and software to accomplish the tasks of digitally acquiring an acoustic signature with the required level of precision and then to analyse it to produce "decision patterns” and "decision functions” which can be used to identify the source of the explosive or impulsive shock wave.
  • a source might be the gun muzzle "break” or the “burst” (fall of shot) from an exploding shell.
  • the preferred system enables such factors as the charge weight and type of gun to be determined.
  • the preferred methods lend themselves to effecting identification in real-time.
  • embodiments of the invention can provide a practical solution to identifying the sources of explosions with a high degree of confidence and possibly using equipment which is more portable, more quickly deployed and more cost-effective than has previously been the case.
  • Figure 1 is a schematic diagram of an embodiment of triggering chamber
  • Figure 2 is a schematic diagram of the principal components of the preferred embodiment of system for identifying the source of an explosive or impulsive shock wave;
  • Figure 3 shows an example of a two-dimensional decision pattern producible by the system of Figure 2;
  • Figure 4 shows an example of a three-dimensional decision pattern producible by the system of Figure 2;
  • Figure 5 shows examples of three-dimensional decision patterns producible by the system of Figure 2 for two different types of artillery
  • Figure 6 a two-dimensional pattern grouping decision function for different types of artillery.
  • triggering device 10 which is formed of a chamber 12 of substantially rectangular cuboid shape.
  • An open end of the chamber 12 is provided with a floating rigid or substantially rigid panel or wall 14, referred herein as an excitation or triggering panel.
  • a supporting framework 16 supports the excitation panel 14 in a floating manner, and can take many forms, such as a channel which provides a loose fit of the panel 14 therein, a deformable support such as a viscoelastic material, or any other suitable form.
  • the excitation (triggering) panel 14 typically of glass or other material with sufficient stiffness and density, is chosen to respond to explosive or impulsive shock waves. It is loosely supported within its framework in such a way that it is free to vibrate.
  • a sound pressure sensor in this example a microphone (not shown), described in further detail below.
  • the actual structure, shape and size of the triggering device 10 can be chosen by simple experiment by the skilled person in dependence upon the particular application.
  • a cubic shape is the simplest to manufacture.
  • a chamber 12 whose internal distance between its walls of 10 to 100 times the diameter of the microphone provides good triggering.
  • FIG. 2 shows the preferred embodiment of identification system.
  • the system includes two transducers, typically microphones, 20, 22, the first of which, transducer 20, is the measurement transducer, while the second transducer 22 is located inside the trigger chamber 12 to act as the trigger sensor.
  • the transducers are preferably high precision, advantageously condenser microphones and most preferably electret-condenser high-precision microphones.
  • the analogue signal received by the two transducers 20, 22 is passed to a digital signal processing (DSP) chip 26 and an analogue-to-digital converter 28 via anti-aliasing filters 24.
  • DSP digital signal processing
  • the initial part of the digitised signal held in memory 32 is added to the main body of the digitised signal 30 to form the digitised time-history data file 34. This is passed to processing units 36 to 46, described in more detail below.
  • acoustic sounds are converted, in this embodiment, into electrical voltages using the electret-condenser high-precision microphones 20, 22.
  • Two microphones are used, one acting as a trigger microphone 22 (positioned inside the triggering chamber 12), the other acting as the measurement microphone 20.
  • Any output from the triggering microphone 22 is passed to the DSP unit 26, which commences acquisition if the signal it receives is of a sufficient voltage level. Following this, the output from the measurement microphone 20 is acquired and digitised by the analogue-to-digital (A/D) converter 28. The initial (pre-triggered) part of the signal (i.e. that which is acquired before the trigger microphone triggers data acquisition) is then added from memory 32 to the beginning of the main digitised time history. A Modified Mach Number 36, as well as other key parameters, is then calculated, using selected portions of the digitised time history signal, as is described in detail below. Following this operation, time windowing is applied and overlaid FFTs 40 are performed. Sound intensity over a predefined frequency bandwidth is then calculated. Finally, a three-dimensional "decision pattern" 44 and “decision function” 46 are produced, showing how certain key parameters compare with those from various types of artillery. From these, the source of the acoustic shock wave signal of interest can be identified.
  • A/D analogue
  • the preferred embodiment of signal processing is now described in detail.
  • the preferred methodology can be considered as including three distinct processes: data acquisition, data analysis and results processing.
  • Acoustic sounds from artillery are first converted into electrical voltages using sensitive high-precision transducers, typically electret-condenser microphones 20, 22.
  • sensitive high-precision transducers typically electret-condenser microphones 20, 22.
  • Such microphones have a flat frequency response over the audio frequency range. They also have the required sensitivity.
  • the outputs from the measurement microphone 20 and triggering microphone 22 are initially routed through anti-aliasing filters 24.
  • a special feature of this embodiment is the "pre-triggered acquisition", allowing the inclusion of the initial part of the signal from the measurement microphone 20 (i.e. that which is acquired before the trigger microphone 22 triggers data acquisition).
  • the excitation (triggering) panel or window 14 is loosely supported within its framework in such as way that it is free to vibrate.
  • the sound field is a combination of the direct field of the source, the reverberant field and emitted sound from panel 14 vibration at the surface of the chamber 12.
  • a portion of the direct field sound from impulsive waves plus the emitted sound from the excitation panel will enter the chamber 12 and be reflected within it. This creates a reverberant field.
  • the total sound energy measured at a point within the chamber 12 is the sum of the sound energy due to the direct field and that due to the reverberant field.
  • the sound pressure level at that point due to the combined effect of the direct and reverberant sound field is:
  • Lw is the sound pressure level generated by transmission from a source
  • D is a characteristic factor related to the position and direction of microphone arrangement within the chamber
  • R is the room/chamber constant.
  • DSP Digital Signal Processing
  • An example would be the Texas TMS series.
  • a sample and hold circuit along with an analogue-to-digital (A/D) converter 28 is provided to enable data acquisition and digitisation.
  • the DSP device 26 receives a positive voltage of a certain level from the trigger microphone 22, data acquisition using the measurement microphone 20 commences for a pre-determined time period.
  • the complete time history 34 is then subjected to various computerised mathematical data analysis operations in order to extract certain key parameters from it, the most important being a new parameter termed the "Modified Mach Number", or "M-Mach number”.
  • a unique feature of the preferred embodiment is the derivation and subsequent application of the "M-Mach number" .
  • Mach number represents the non-dimensional speed of shock wave front propagation, being a function of the sound over-pressure level of the shock wave and of atmospheric pressure as well as temperature.
  • the Mach number of a shock wave is also a function of temperature, atmospheric pressure and measured over-pressure level at the receiving point. It represents the unique acoustic characteristics of the resulting shock front and is affected by many factors, such as the distance between receiving point and the centre of source of sound, temperature, atmosphere pressure and other meteorological conditions.
  • Mach number is a dimensionless ratio N/a, the speed of the wave front (V) over the speed of sound (a).
  • a mathematical equation of Mach number in terms of peak sound pressure of the blast wave front can be deduced from analysing the pressure change when an air stream flows through the stepped wave front.
  • the Modified Mach number can be interpreted as being proportional to the force necessary to stop the fluid over the force necessary to compress it by a certain fraction. It may be defined as:
  • Mach ref is based on the smallest number the DSP system 26 can measure (that is, the system resolution).
  • the level of M-Mach indicates the proportion of force that compresses the air ahead of the blast wave front and overcomes the force for stopping the blast wave propagation. This is a function of the total energy of the blast wave and the inertia of the wave mass.
  • This process generates 44, 46 two-dimensional "decision patterns” and both two- and three-dimensional "decision functions”.
  • a time average of the overlaid FFT 40 is calculated over a defined frequency bandwidth, from which the Sound Intensity Level (SIL) is deduced, as follows:
  • SILi is the calculated sound intensity level for a frequency range from f to (fi + ⁇ f), that is over a predefined bandwidth:
  • SPLover 20 times the logarithm of the ratio between measured sound pressure and reference sound pressure.
  • the measured sound pressure Pover is called the sound over pressure, which is the absolute sound pressure minus the atmospheric pressure.
  • Modified Mach number represents the acoustic speed of the wave front of a shock wave
  • Sound Intensity Level within a narrow frequency bandwidth the total sound energy (as a time average) within that frequency bandwidth;
  • Decision Function this is deduced from the Decision Pattern. Its role is to aid in the identification of type of guns/explosions. Automatic artillery classification can be effected if based upon this function.
  • the "decision pattern” and “decision function” plots can be compared with those from known sources of explosions, such as various types of artillery. Thus, the source of the acoustic signal under scrutiny can be identified.
  • a two-dimensional "decision pattern" is shown for three different types of artillery.
  • the decision patterns consist of a series of markers.
  • the Y co-ordinate of any marker represents its sound energy level within that frequency band. Joining all the markers with a straight line forms a decision pattern for that type of artillery event.
  • the x co-ordinate of a marker will depend upon its Modified Mach number.
  • the magnitude of the Modified Mach number indicates either the artillery charge weight or the distance from which the event has emanated.
  • Figure 4 shows two and three-dimensional "decision functions", in which the 2-D decision function is based upon the third Frequency Bandwidth Number of the first of the two 3-D decision functions shown.
  • the two axes are Acoustic Shock Wave Energy Potential and Modified Mach Number.
  • 2-D plots of this kind assist in the discrimination process.
  • different event types are clearly represented as bands or groups.
  • 3-D Decision Function Plots give a good overall view. It can also be seen that different artillery types can be grouped. The three axes for these plots are Acoustic Shock Wave Energy Potential, Modified Mach Number and Frequency Bandwidth Number.
  • This methodology can be used to discriminate between gun/artillery fire ("breaks") and fall of shot (“bursts”) from individual types of artillery, as well as other sources of explosions.
  • Figures 5 and 6 show examples of two- and three-dimensional decision pattern producible by two different types of artillery.
  • the described system can be used to identify other acoustic signatures, such as those from small-arms, air/sea/ground vehicles; indeed of any device or event which produces an impulsive sound.
  • the described embodiments provide a system, consisting of hardware and software, with the capability of acquiring an acoustic signature with high precision and ultimately producing "Decision Patterns” and “Decision Functions", which can be used to identify artillery or other sources of shock waves from their acoustic signatures.
  • the microphones include two transducers (typically high-performance microphones, such as condenser microphones), one of which acts as a triggering microphone.
  • This microphone is harboured within a special enclosure containing a panel or wall, which is inserted in such a way that it is free to vibrate slightly.
  • a combination of the direct field of the source, the reverberant field and the emitted sound from panel vibration at the surface of the enclosure corresponding to a certain voltage threshold will cause triggering and data acquisition to commence.
  • the anti-alias filtered, digitised signal from the (other) measurement microphone is then processed in such a manner that certain parameters can be extracted. The most significant of these parameters are the "Modified Mach Number”, the "Sound Intensity Level", the "Acoustic Shock Wave Energy

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • Remote Sensing (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

L'invention concerne un système doté de la capacité à acquérir une signature acoustique avec une précision élevée, pouvant être utilisé pour identifier une artillerie ou d'autre sources d'onde de choc explosive à partir de leur signature acoustique. Ce système comprend deux microphones (20, 22) à performances élevées, l'un agissant en tant que microphone déclencheur (22). Ce microphone (22) est placé dans une chambre spéciale (12) contenant un panneau ou une paroi flottante (14), inséré de telle façon à pouvoir librement vibrer légèrement. Tout signal acoustique impulsionnel provoque l'établissement d'une pression interne d'impulsion qui fait démarrer une acquisition de données. Après filtrage anti-repliement et numérisation, le signal provenant du microphone de mesure (20) est traité de telle manière que l'on peut en extraire certains paramètres. Les plus significatifs de ces paramètres sont le 'nombre de Mach modifié', le 'niveau d'intensité sonore', le 'potentiel d'énergie d'onde de choc acoustique' et le 'nombre de largeur de bande de fréquence'. Ils peuvent être portés sur un graphique afin de produire une 'structure de décision' bidimensionnelle et une 'fonction de décision' bidimensionnelle ou tridimensionnelle, qui peuvent être utilisées afin d'identifier l'origine de l'onde choc impulsionnelle ou explosive.
EP01965444A 2000-09-13 2001-09-11 Procede et appareil d'identification de la source d'un evenement impulsionnel ou explosif Withdrawn EP1317678A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0022488A GB0022488D0 (en) 2000-09-13 2000-09-13 Method apparatus for identifying the source of an impulsive or explosive ev ent
GB0022488 2000-09-13
PCT/GB2001/004086 WO2002023221A2 (fr) 2000-09-13 2001-09-11 Procede et appareil d'identification de la source d'un evenement impulsionnel ou explosif

Publications (1)

Publication Number Publication Date
EP1317678A2 true EP1317678A2 (fr) 2003-06-11

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Application Number Title Priority Date Filing Date
EP01965444A Withdrawn EP1317678A2 (fr) 2000-09-13 2001-09-11 Procede et appareil d'identification de la source d'un evenement impulsionnel ou explosif

Country Status (4)

Country Link
EP (1) EP1317678A2 (fr)
AU (1) AU2001286085A1 (fr)
GB (1) GB0022488D0 (fr)
WO (1) WO2002023221A2 (fr)

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Publication number Priority date Publication date Assignee Title
USRE42281E1 (en) 2000-09-11 2011-04-12 Hamamatsu Photonics K.K. Scintillator panel, radiation image sensor and methods of producing them
CN110095493A (zh) * 2019-03-21 2019-08-06 南京理工大学 一种爆炸物的检测方法
CN113884951B (zh) * 2021-10-22 2024-04-30 广东电网有限责任公司 电容元件监测方法、装置和系统

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Publication number Priority date Publication date Assignee Title
DE3116586A1 (de) * 1981-04-27 1984-03-08 Fried. Krupp Gmbh, 4300 Essen Verfahren zum ermitteln von geschuetzstandorten
US5544129A (en) * 1994-08-30 1996-08-06 Aai Corporation Method and apparatus for determining the general direction of the origin of a projectile
IL112730A (en) * 1995-02-21 2000-02-17 Israel State System and method of noise detection
US5917775A (en) * 1996-02-07 1999-06-29 808 Incorporated Apparatus for detecting the discharge of a firearm and transmitting an alerting signal to a predetermined location
US5930202A (en) * 1996-11-20 1999-07-27 Gte Internetworking Incorporated Acoustic counter-sniper system

Non-Patent Citations (1)

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Title
See references of WO0223221A3 *

Also Published As

Publication number Publication date
AU2001286085A1 (en) 2002-03-26
GB0022488D0 (en) 2001-09-19
WO2002023221A3 (fr) 2002-08-01
WO2002023221A2 (fr) 2002-03-21

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