EP0233390A1 - Procédé et dispositif pour distinguer des bruits causés par le bris de verre - Google Patents

Procédé et dispositif pour distinguer des bruits causés par le bris de verre Download PDF

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Publication number
EP0233390A1
EP0233390A1 EP86301025A EP86301025A EP0233390A1 EP 0233390 A1 EP0233390 A1 EP 0233390A1 EP 86301025 A EP86301025 A EP 86301025A EP 86301025 A EP86301025 A EP 86301025A EP 0233390 A1 EP0233390 A1 EP 0233390A1
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EP
European Patent Office
Prior art keywords
low frequency
high frequency
sound
glass
signal
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Withdrawn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
EP86301025A
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German (de)
English (en)
Inventor
Raymond John Davenport
Michael Andrew Tomlinson
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.)
Automated Security Holdings Ltd
Original Assignee
Automated Security Holdings 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 Automated Security Holdings Ltd filed Critical Automated Security Holdings Ltd
Priority to EP86301025A priority Critical patent/EP0233390A1/fr
Publication of EP0233390A1 publication Critical patent/EP0233390A1/fr
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/02—Mechanical actuation
    • G08B13/04—Mechanical actuation by breaking of glass

Definitions

  • This invention relates to a method and an apparatus for detecting sounds due to the breakage of glass.
  • the sound of breaking glass is usually readily identifiable to the human ear, the physical make-up of the sound depends on such matters as the thickness and area of the glass, the manner in which it is mounted ,the height above floor level and the acoustic properties of the enclosure in which the breakage takes place. These factors make the identification of the sound from its physical characteristics, difficult and uncertain.
  • the sound of breaking glass comprises an initial low frequency sound of fairly large amplitude followed by higher frequency sound as the fragments of glass collide with one another and with the floor.
  • U.S. Patent 4,134,109 proposes analysing the pattern of acoustic signals in terms of signal strength of the initial sound and frequency content of subsequent sounds to discriminate between the breaking of glass and other sounds. If the amplitude of the initial sounds exceeds a given threshold and the frequency content of the later sound fits a predetermined pattern, an alarm signal is produced.
  • U.S. 4,134,109 includes a complicated signal analysis circuit which is costly. Another disadvantage is the inability to discriminate between repeated large amplitude sounds containing high frequency components. It can be triggered by any sufficiently loud sound irrespective of its frequency.
  • An object of the present invention is to avoid the disadvantages inherent in the prior art and to provide a method of and apparatus for detecting sounds due to the breakage of glass, which is simple and relatively inexpensive and can reliably discriminate between the sound of breaking glass and other sounds.
  • a method of discriminating sounds due to the breakage of glass by converting the sounds into an electrical signal and analysing the signal, the method comprising detecting the occurrence of an initial sound, selecting only those initial sounds having components in a low frequency band and preferably exceeding a predetermined threshold level, establishing thereupon a delay followed by a time window, detecting the occurrence within the time window of a subsequent sound having frequency components in a high frequency band and generating an output signal if, and only if, the signals are detected in the required order and timing.
  • apparatus for carrying out the above method comprising a transducer, a low frequency channel including a bandpass filter, a high frequency channel including a bandpass filter, first and second delay circuits, and an AND gate and alarm means , the transducer providing signals to the low frequency and high frequency channels, an output signal from the low frequency channel being applied to the first delay circuit, and the delayed output being applied to one input of the AND gate for a duration set by the second delay circuit, an output signal from a high frequency channel being applied to the second input of the AND gate, and the coincidence signal from the AND gate tripping the alarm means.
  • the present inventors have discovered that the initial sound due to the breakage of glass has substantial (i.e. salient) frequency components at about 350 Hz and the subsequent sounds due to the falling pieces of glass have substantial frequency components at about 6.5 KHz. They have found that these frequencies are characteristic of breaking glass and are substantially independent of the other variable factors mentioned above such as size and thickness of glass, height and nature of mounting etc.
  • the low frequency band may extend up to about 800 or 900 Hz, it is preferably centred on a frequency of substantially 350 Hz.
  • a suitable value for the bandwidth of the higher frequency signal is 4 KHz to 10 KHz.
  • the high frequency band is centred upon 6.5 KHz and has a bandwidth of ⁇ 2KHz.
  • the time window may suitably start at 200 milliseconds after the detection of the low frequency signal and continue for a further 800 milliseconds.
  • Figure 1 shows a waveform of a typical sound due to the breaking of a pane of glass. It comprises two major components, namely the transient sound generated when the pane of glass is struck (referred to herein as the "thump") followed after an interval by the sound due to the collision of the glass fragments with each other and with the surface upon which they fall (referred to herein as the "tinkle”), this being a sound of lower amplitude.
  • the frequency spectra of these two components are respectively shown in Figures 2a and 2b.
  • the present invention turns on the discovery that the thump has strong frequency components in the neighbourhood of 350 Hz and the tinkle has substantial frequency components in the neighbourhood of 6.5 KHz. These values being characteristic of breaking glass and substantially independent of the variable factors mentioned above.
  • the invention makes use of these facts by detecting the occurrence of components at these frequencies in that order, and separatedby a brief time interval.
  • Figure 3 indicates schematically the response of a detection system according to the present invention.
  • A the low frequency components are detected and this initiates a short time delay, shown as A in the Figure.
  • B a time window is established, indicated at B in the Figure, during which the higher frequency of the tinkle components, if detected, is caused to produce a signal, for example, for setting off an alarm.
  • a microphone 1 is positioned near the glass to be protected and its output is fed into two channels, a low frequency and a high frequency channel.
  • the low frequency channel comprises a low frequency bandpass filter 2 with a centre frequency of 350 Hz, followed by an amplifier 3 and a voltage comparator 4 which provides an output voltage when the amplitude of the signal from the bandpass filter and amplifier exceeds a threshold value determined by the setting of potentiometer R15.
  • the signal from the comparator 4 indicating that frequency components in the region of 350 Hz possibly representing the thump portion of a glass breakage signal have been detected is applied to a mono-stable 5 which, after a 200 millisecond delay triggers a timer 6. This timer produces a signal lasting for 800 milliseconds and this signal enables an AND gate 7.
  • the signal from the microphone 1 is also applied to a high frequency channel.
  • This comprises a high frequency bandpass filter 8 having a pass band centred on 6.5 KHz and a bandwidth of ⁇ 2 KHz, followed by a frequency to voltage converter circuit 9, the output of which is applied to a one input of a voltage comparator 10. It will not allow any signal below 4.5 KHz to generate an output. It will be understood that the high frequency band pass filter 8 merely attenuates signals at frequencies outside the bandwidth and does not exclude them altogether. This is why the frequency to voltage converter is needed. It enables discrimination to be made between noises such as caused by tapping on the window, which contains dominant low frequency components in addition to high frequency components, and the tinkle in which the dominant frequencies are high frequencies above 4.5 KHz. This further reduces the risk of false alarms.
  • a signal is applied to other input of the AND gate 7.
  • the reference value is set during manufacture and assembly of the detector, by means of the potential divider comprising R28 and R30. Further adjustment of the point at which the comparator 10 triggers (ie. the sound pressure threshold level) is available by varying the gain of the high band pass filter 8 and amplifier 9 circuits using variable resistor R24.
  • the AND gate 7 thus receives a signal at one input during a time window extending from 200 milliseconds to one second after a 350 Hz input signal possibly representing the thump of a glass breakage, has been received and a signal at its other input indicating detection of a signal having a component at 6.5 KHz. The coincidence of these two signals within the correct time frame produces an output from the AND gate 7 indicating that breakage has taken place.
  • the signal from the AND gate 7 is fed to a latch circuit 11 which operates an alarm indicator circuit 12 illuminating a light, and also to a relay circuit 13 arranged to give an audible or other warning.
  • a reset circuit 14 is provided to reset the latch 11 and the timer circuits, and this may be operated from the control circuit or from a remote push button.
  • the power for operating the circuit is provided by a power pack 14.
  • One advantage of detecting the sound of breaking glass in accordance with the present invention is that the need for time consuming tuning of the detector circuit on site, after installation, is avoided. Tests have shown that the threshold levels against which the signals are compared in comparators 4 and 10, equivalent to a low frequency sound pressure level of about 95dB and a high frequency sound pressure level of about 75dB give satisfactory results and these threshold levels can be set in the factory during manufacture and assembly.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)
EP86301025A 1986-02-14 1986-02-14 Procédé et dispositif pour distinguer des bruits causés par le bris de verre Withdrawn EP0233390A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP86301025A EP0233390A1 (fr) 1986-02-14 1986-02-14 Procédé et dispositif pour distinguer des bruits causés par le bris de verre

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP86301025A EP0233390A1 (fr) 1986-02-14 1986-02-14 Procédé et dispositif pour distinguer des bruits causés par le bris de verre

Publications (1)

Publication Number Publication Date
EP0233390A1 true EP0233390A1 (fr) 1987-08-26

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ID=8195888

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86301025A Withdrawn EP0233390A1 (fr) 1986-02-14 1986-02-14 Procédé et dispositif pour distinguer des bruits causés par le bris de verre

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EP (1) EP0233390A1 (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0499148A1 (fr) * 1991-02-11 1992-08-19 Pittway Corporation Détecteur de bris de verre
WO1993019385A1 (fr) * 1992-03-24 1993-09-30 Rover Group Limited Dispositif et procede de surveillance d'un espace
EP0592191A1 (fr) * 1992-10-07 1994-04-13 Guardall Limited Circuit d'activation
EP0605993A2 (fr) * 1993-01-07 1994-07-13 Ford Motor Company Système de senseurs de sécurité pour véhicule à moteur
DE19521194A1 (de) * 1995-06-10 1996-12-12 Telefunken Microelectron Verfahren zum Überwachen der von Glasscheiben bedeckten Öffnungen eines geschlossenen Raumes
US5608377A (en) * 1995-10-20 1997-03-04 Visonic Ltd. Acoustic anti-tampering detector
WO1997009701A1 (fr) * 1995-09-01 1997-03-13 Digital Security Controls Ltd. Dispositif pour detecter le bris d'une vitre
GB2284668B (en) * 1993-12-01 1998-04-01 Visonic Ltd Glass breakage detector
GB2434876A (en) * 2006-02-01 2007-08-08 Thales Holdings Uk Plc Frequency and time audio signal discriminator
JP2014016725A (ja) * 2012-07-06 2014-01-30 Panasonic Corp 侵入検知装置
US9188487B2 (en) 2011-11-16 2015-11-17 Tyco Fire & Security Gmbh Motion detection systems and methodologies

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4091660A (en) * 1977-03-16 1978-05-30 Matsushita Electric Industrial Co., Ltd. Apparatus for detecting the breaking of a glass plate
US4134109A (en) * 1977-05-16 1979-01-09 Omni Spectra, Inc. Alarm system responsive to the breaking of glass
GB1577941A (en) * 1977-08-19 1980-10-29 Rca Corp Glass break defectors
GB2080592A (en) * 1980-07-03 1982-02-03 Rca Security Systems Ltd Vibration and/or impact detection system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4091660A (en) * 1977-03-16 1978-05-30 Matsushita Electric Industrial Co., Ltd. Apparatus for detecting the breaking of a glass plate
US4134109A (en) * 1977-05-16 1979-01-09 Omni Spectra, Inc. Alarm system responsive to the breaking of glass
GB1577941A (en) * 1977-08-19 1980-10-29 Rca Corp Glass break defectors
GB2080592A (en) * 1980-07-03 1982-02-03 Rca Security Systems Ltd Vibration and/or impact detection system

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0499148A1 (fr) * 1991-02-11 1992-08-19 Pittway Corporation Détecteur de bris de verre
GB2279748A (en) * 1992-03-24 1995-01-11 Rover Group A device for and method of surveillance of a space
WO1993019385A1 (fr) * 1992-03-24 1993-09-30 Rover Group Limited Dispositif et procede de surveillance d'un espace
GB2279748B (en) * 1992-03-24 1996-07-24 Rover Group A device for and method of surveillance of a space
EP0592191A1 (fr) * 1992-10-07 1994-04-13 Guardall Limited Circuit d'activation
EP0720938A3 (fr) * 1993-01-07 1996-12-18 Ford Motor Co Système de capteurs de sécurité pour véhicule à moteur
EP0720938A2 (fr) * 1993-01-07 1996-07-10 Ford Motor Company Système de capteurs de sécurité pour véhicule à moteur
EP0605993A3 (fr) * 1993-01-07 1994-08-31 Ford Motor Co
EP0605993A2 (fr) * 1993-01-07 1994-07-13 Ford Motor Company Système de senseurs de sécurité pour véhicule à moteur
US5510765A (en) * 1993-01-07 1996-04-23 Ford Motor Company Motor vehicle security sensor system
GB2284668B (en) * 1993-12-01 1998-04-01 Visonic Ltd Glass breakage detector
US5917410A (en) * 1995-03-03 1999-06-29 Digital Security Controls Ltd. Glass break sensor
DE19521194A1 (de) * 1995-06-10 1996-12-12 Telefunken Microelectron Verfahren zum Überwachen der von Glasscheiben bedeckten Öffnungen eines geschlossenen Raumes
WO1997009701A1 (fr) * 1995-09-01 1997-03-13 Digital Security Controls Ltd. Dispositif pour detecter le bris d'une vitre
AU708497B2 (en) * 1995-09-01 1999-08-05 Tyco Safety Products Canada Ltd Glass break sensor
US5608377A (en) * 1995-10-20 1997-03-04 Visonic Ltd. Acoustic anti-tampering detector
GB2434876A (en) * 2006-02-01 2007-08-08 Thales Holdings Uk Plc Frequency and time audio signal discriminator
GB2434876B (en) * 2006-02-01 2010-10-27 Thales Holdings Uk Plc Audio signal discriminator
US9188487B2 (en) 2011-11-16 2015-11-17 Tyco Fire & Security Gmbh Motion detection systems and methodologies
JP2014016725A (ja) * 2012-07-06 2014-01-30 Panasonic Corp 侵入検知装置

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