US3898640A - Method and apparatus for providing space security based upon the acoustical characteristics of the space - Google Patents

Method and apparatus for providing space security based upon the acoustical characteristics of the space Download PDF

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Publication number
US3898640A
US3898640A US382192A US38219273A US3898640A US 3898640 A US3898640 A US 3898640A US 382192 A US382192 A US 382192A US 38219273 A US38219273 A US 38219273A US 3898640 A US3898640 A US 3898640A
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United States
Prior art keywords
space
compressional
oscillations
frequency range
changes
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US382192A
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English (en)
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Erich Hossbach
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FASER-UND KUNSTSTOFF PRESSWERK ROMEN KG
ROMEN FASER KUNSTSTOFF
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ROMEN FASER KUNSTSTOFF
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/16—Actuation by interference with mechanical vibrations in air or other fluid
    • G08B13/1609—Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/16—Actuation by interference with mechanical vibrations in air or other fluid
    • G08B13/1654—Actuation by interference with mechanical vibrations in air or other fluid using passive vibration detection systems
    • G08B13/1681—Actuation by interference with mechanical vibrations in air or other fluid using passive vibration detection systems using infrasonic detecting means, e.g. a microphone operating below the audible frequency range

Definitions

  • a security measure such as an alarm unit, is triggered responsive to the de- 5 References Cited tected non-directional sound wave field in response to UNITED STATES PATENTS a minute change in the confines of the room to be protected, but not in response to movements in the room.
  • 2,031,951 2/1936 Hartley 340/258 C 2,071,933 2/ l937 Miessner 340/258 B 11 Claims, 6 Drawing Figures FEEDBACK 24 ALARM GE in 1 PROTECTED SPACE GEN I ⁇ DIFFERENTIAL V 77 AMPLIFIER ADJUSTING 23 RESISTOR I 2 CIPHER GEN.
  • the present invention relates to methods of and devices for providing space or room security by means of BACKGROUND OF THE INVENTION It is well known, in the context of the provision of security for a space, to generate in said space by means of an acoustic radiator an audio frequency or ultrasonic acoustic field, the vibrations generated being reflected from the walls of the space and changes in said field being utilized to trigger security measures.
  • the Doppler effect is exploited and utilized to indicate objects moving in the space. It is also known to utilize frequencies in the audible range and to locate the acoustic pick-up in the space in such a way that when any disturbance in the acoustic field or sound pattern occurs due to changes in reflection conditions, an alarm signal is triggered. Finally, it is known to exploit the infrasound vibrations occurring with the opening and closing of doors or windows, and to employ a flame detector or a pressure gauge to detect this and provide an indication.
  • the object of the present invention is to provide a method and a device which makes use of a nondirectional acoustic field completely filling the space, which cannot be detected by the intruder and which responds to tiny changes in the confines of the space, but not to movements therein.
  • the present invention provides a method of providing security protection for a space or room comprising the steps of generating a non-directional sound wave field to occupy substantially completely the space to be protected, and detecting the non-directional sound wave field.
  • the non-directional sound wave field is inaudible to a human intruder into the space to be pro tected.
  • a security measure is triggered responsive to the detected nondirectional sound wave field in response to a minute change in the confines of the space to be protected, but not in response to movements therein.
  • the present invention also provides a device for implementing the aforestated method.
  • the device includes a generator which radiates frequencies which are located in the infrasound range, or are equal to or lower than the highest natural resonant frequency of the space being protected, or are located within the flanks of the resonance curve defined by the natural resonant frequency.
  • An acoustic pick-up transmits infrasonic frequencies and, in the case of wavelengths which are longer than the dimensions of the space being protected, is arranged at an arbitrary point in the space, or, in the case of wavelengths which correspond to the space dimensions, is arranged in the neighborhood of the boundary walls.
  • An object of the present invention is to make it possible to secure a space without it being necessary to effect a completely airtight closure thereof, although opening of the space or any other change in the boundaries thereof will trigger an alarm.
  • this result is achieved in that the generator producing the acoustic field radiates frequencies which are located in the infrasound range or are equal to or lower than the highest natural resonance frequency of the space being protected, or again are located within the flanks of the resonance curve defined by the natural resonance frequency, and in that the changes in the phase alone of the acoustic field, or changes associated with the amplitude and frequency therein, are employed for monitor-
  • This method has the advantage that the acoustic field which is radiated, for example, by a vibration generator at very low frequency (in the order of magnitude of at and below the audible threshold of 15 Hz), protects the entire space because any change in the confines or boundaries of the space produces a change in the acoustic conditions so that phase changes or also frequency or amplitude changes result which can be employed to trigger the alarm systems.
  • FIG. 1 is a pictorial illustration of a space or room which is to be protected provided with the device in accordance with the invention.
  • FIG. 2 is a block circuit diagram of a design using a microphone, loudspeaker and audio generator.
  • FIG. 3 is a block circuit diagram of a self-excited design using microphone and loudspeaker, with selfexcitation through amplified feedback via microphone and loudspeaker.
  • FIG. 4 is a block circuit diagram of an arrangement equipped with loudspeaker and generator, the loudspeaker also doing duty as a microphone.
  • the so-called reaction is analyzed by the discriminator comprising a differential amplifier, after differentiation of the voltage across the generator and the generator series resistor (13).
  • FIG. 5 is a block circuit diagram of an arrangement with a loudspeaker for example, in which the loudspeaker also does duty as a microphone (as in FIG. 4) and is self-exciting (as in FIG. 3) by feedback.
  • FIG. 6 is a diagram of the ratio of resonance frequency to space size, pertaining to various sizes of areas on the part of the openings in the confines of the space.
  • the device 1 shown in FIG. I is located in a room or space 2 which is to be protected, which may, for example, include doors 3 and/or windows 4 and 4.
  • the device I can be erected or positioned at virtually any point in the space.
  • the loudspeaker acts as a radiator and operates in the same space without any development of dead areas. If, for example, the space is one having a volume of 3 cu.m., e.g., the passenger space of a motor car, then in accordance with the diagram shown in FIG. 6, with an opening area of 200 sq.cm. (keyholes, cracks, air vents, heating vents, etc.) the natural frequency is around 15 Hz.
  • the unit must therefore be tuned to 15 cycles/sec.
  • the device shown in FIG. 2 in the block circuit diagram contains an audio generator 11 which excites a loudspeaker 14 through an amplifier 12.
  • the loudspeaker I4 is located in the space 15 being protected.
  • there is a microphone 16 which is connected through an amplifier 18 to a differential amplifier 20.
  • To this differential applifier 20 from the output of the amplifier l2 vibrations generated by the audio generator 11 are applied directly across an adjusting or variable resistor 17.
  • the amplifier 20 is provided with selective negative feedback 21.
  • the differential amplifier 20 and the negative feedback 21 together act as a discriminator vis-a-vis frequency, amplitude and phase.
  • the alarm unit 24 e.g., a horn or an optical alarm signal, is connected.
  • the alarm inhibit and release switch 22 is connected to a signal generator 23 which can be controlled by radio, using a cipher generator 25.
  • the device operates in the following way:
  • the acoustic vibrations generated by the loudspeaker l4 excite the space 15 at its resonant frequency.
  • the acoustic vibrations picked up by the microphone 16, after amplification, are applied to the differential amplifier 20, with the negative feedback 21, acting as amplitude, frequency and phase discriminator.
  • the differential amplifier 20 With the help of the resistor 17, the differential amplifier 20 is so adjusted that when the space 15 is excited at its natural frequency, no output signal is produced of a kind which can trigger the alarm device 24.
  • the operator before leaving the space 15, sets up the device in this way, the switch 22 still keeping the unit disconnected. After the space 15 has been left, the switch 22 is so operated by means of the generator 25 that the discriminator is connected to the alarm device 24.
  • FIG. 3 is distinguished from FIG. 2 by the fact that instead of the audio generator 11, self-excitation is produced by a return of the output voltage from the amplifier 18 through the variable resistor or controller 17 to the input of the generator amplifier 12.
  • FIG. 4 is distinguished from FIG. 2 by the fact that the voltage otherwise obtained from the microphone is picked off from the loudspeaker I4 and a generator 11 alone, therefore, without any microphone 16.
  • the socalled feedback is analyzed by the discriminator, comprising differential amplifier 20 and the selective negative feedback 21, after differentiation of the voltage across the transmitted and the transmitter series resistor 13.
  • FIG. 5 is distinguished from FIG. 4 by the fact that no generator 11 is used, instead simply the loudspeaker 14 on its own and the generator amplifier 12 being exciting as in FIG. 3 by feedback.
  • FIG. 6 a diagram has been illustrated on the ordinate of which the frequency in cycles per second has been plotted, showing that a space with a cubic capacity V, indicated by the oblique lines, will vibrate at the natural resonant frequency, when the space has the opening area in square cms., indicated on the abscissa. If a space of 10 mm. has, for example, openings with a total area of about 250 sq.cm., then its natural resonant frequency is 10 cycles/sec.
  • the resonant frequency shifts i.e., the phase and amplitude of the vibration (oscillation) applied to the differential amplifier 20 from the amplifier 18 change so that the differential amplifier 20 is displaced from the equilibrium state in which it has been set up.
  • This deviation is detected by the discriminator 20 and is used to trigger the alarm unit 24.
  • even a slight increase in the opening area in the wall of the space 2 or 15 is sufficient to produce an adequate change in the resonant conditions.
  • a timer switch can be used which is set up before leaving the space 2 or 15 in such a way that the unit switches itself ON after a short time, the switch OFF time being so arranged that the switch 22 is open again before the space 2 or 15 is re-entered.
  • This design, employing a timer switch. has the advantage that no manipulation can be employed to externally render the protection inoperative.
  • Wind blowing through these openings from the outside can, it is true, produce a change in air pressure in the space being detected, but cannot produce any detuning of the acoustic situation.
  • a generator which is located in the same space, or also, for that matter, by the use of one which is located outside the space and connected by acoustic coupling through the space itself, i.e., produces coupling by being built into a wall, into a ceiling, located in an air duct, in a chimney flue or in a stairwell.
  • a generator can monitor several spaces, provided that these can develop standing waves at the same wavelength and that there is acoustic coupling because the frequency used is very low and in order to attenuate su'chlow frequencies acoustic absorber elements are required which are a meter thick.
  • a device for implementing the method contains, for example, an acoustic generator which generates the acoustic vibrations filling the space, and an acoustic pick-up, e.g., a microphone, which responds to changes in phase alone, or to associated changes in amplitude and frequency on the part of the acoustic vibrations in response to changes in the conditions in the space.
  • an acoustic pick-up e.g., a microphone
  • the frequency of the audio generator is chosen to be so low, or the amplitude of the radiated sound so small, that the acoustic vibrations are located outside the audible range. It is particularly advantageous to tune the frequency of the audio generator to the natural resonance frequency of the space being protected.
  • values are available, as a result of experience in this field, for completely closed spaces, and for spaces which are partly closed and partly open.
  • a space which is completely closed and contains no opening whatsoever should preferentially be protected by means of standing waves, the wavelength, for example, being twice that of an axis of the space or room.
  • the space protection system is particularly sensitive if the radiated sound is tuned to the space resonant frequency or if the frequency is located on a flank of the natural resonance frequency curve, because the various changes are greatest when operating on the resonance curve flank. Even the slightest opening of the door or window, shifting the resonance frequency by the tiniest amount, results in a change in the phase and in a steep drop in the amplitude of the vibration. There is radical attenuation as a consequence of pressure compensation, and in addition to the amplitude, the phase of the vibrations changes in a mannerwhich is easy to measure.
  • the resonance frequency i.e., the wavelength
  • phase i.e., a time shift between radiated and received waves.
  • the equipment cannot be deceived by acoustic manipulation from outside the space.
  • a sensitive microphone i.e., a so-called minispy
  • a more powerful generator to feed it in through a device, such as a loudspeaker, or an amplifier amplifying the received signal picked-up by the minispy.
  • a device such as a loudspeaker, or an amplifier amplifying the received signal picked-up by the minispy.
  • an intruder could readily determine the protection frequency, it is very difficult indeed for him to avoid a change in amplitude when utilizing this procedure.
  • the equipment can be designed as a portable unit, independent of the mains, yielding the particular advantage that a fixed installation in the space, as, for example, the installing of light (etc.) barriers is unnecessary.
  • the unit can also be connected to the mains if required.
  • the unit can be connected through a valve device, e.g., a diode in the case of dc, (on much the same lines as in a motor vehicle), so that the plant cannot be rendered inoperative either by disconnection or by short-circuiting the external source in the plant, the equipment of course having to have its own small current source, although this is available anyway with all standard production portable car radios.
  • the unit will conveniently be so designed that it indicates the state of its own current source and, if this is fluctuating or inoperative, cannot be switched ON. This provides protection against the possibility that an intruder may prepare for a break-in by secretly removing the current source of the protection unit, during an unprotected time.
  • the unit can be switched ON and OFF by a timer switch. It is also possible, for switch-ON and switch-OFF, to utilize a special lock or a shortrange radiator which is tuned to a specific code incorporated into the unit and can be used to switch the unit ON and OFF.
  • generator (loudspeaker) and pick-up (microphone) plus vibration generator;
  • any vibratory device located in the air for example, a loudspeaker, could be used.
  • a method of providing a security protection for a space comprising the steps of:
  • the method of claim 1 further including the step of saturating said space and a second space with said compressional oscillations in the infrasonic frequency range to simultaneously protect both spaces, said second space having an effective volume which is substantially equal to said effective volume of said firstmentioned space.
  • a method according to claim I further including the step of:
  • a system for providing security for a space comprising:
  • said means for detecting is responsive to frequency changes in the fundamental compressional wave of said compressional oscillations in the infrasonic frequency range when said effective volume changes.
  • said means for detecting includes a differential amplifier and a selective negative feedback in electrical communication therewith said amplifier and said feedback cooperating to define a discriminator.

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  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)
US382192A 1972-07-31 1973-07-24 Method and apparatus for providing space security based upon the acoustical characteristics of the space Expired - Lifetime US3898640A (en)

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DE2237613A DE2237613C3 (de) 1972-07-31 1972-07-31 Verfahren und Vorrichtung zur Raumsicherung

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JP (1) JPS4980896A (enrdf_load_html_response)
BR (1) BR7305723D0 (enrdf_load_html_response)
DE (1) DE2237613C3 (enrdf_load_html_response)
FR (1) FR2195017B3 (enrdf_load_html_response)
GB (1) GB1420043A (enrdf_load_html_response)
HU (1) HU167448B (enrdf_load_html_response)
IT (1) IT991881B (enrdf_load_html_response)
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4229811A (en) * 1978-11-09 1980-10-21 General Electric Company Intrusion detection method and apparatus
US4260980A (en) * 1979-04-30 1981-04-07 Bates Mitchell G Blind spot detector for vehicles
EP0286897A1 (de) * 1987-04-09 1988-10-19 Cerberus Ag Verfahren und Vorrichtung zur Überwachung von geschlossenen Räumen
US4853690A (en) * 1986-04-03 1989-08-01 Richard Hirschmann Radiotechnisches Werk Security alarm process and apparatus
US5266905A (en) * 1992-05-29 1993-11-30 Audio Research Corporation Audio amplifier with amplified feedback
EP0909960A3 (de) * 1997-09-16 1999-05-19 f+g megamos Sicherheitselektronik GmbH Ultraschall-Überwachungseinrichtung zum Überwachen eines kfz-Innenraumes
EP0916969A3 (de) * 1997-11-11 1999-11-03 GRUNDIG Aktiengesellschaft Autoradioalarmanlage
US20080224863A1 (en) * 2005-10-07 2008-09-18 Harry Bachmann Method for Monitoring a Room and an Apparatus For Carrying Out the Method
US20110141283A1 (en) * 2009-12-14 2011-06-16 Electronics And Telecommunications Research Institute Security system and method using measurement of acoustic field variation
US10741037B2 (en) * 2018-05-16 2020-08-11 Avaya Inc. Method and system for detecting inaudible sounds

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2523339A1 (fr) * 1982-03-12 1983-09-16 Guglielmetti Vg Electro Dispositif de detection a capteur volumetrique a infra-sons et procede de detection par infra-sons
GB8323685D0 (en) * 1983-09-03 1983-10-05 Gen Electric Co Plc Monitoring displacement
CH667932A5 (de) * 1985-05-24 1988-11-15 Cerberus Ag Nahbereichsueberwachungsgeraet mit schallquelle.
GB8617124D0 (en) * 1986-07-15 1986-08-20 Mace R J Vehicle protection apparatus
GB9812842D0 (en) 1998-06-16 1998-08-12 Ncr Int Inc Automatic teller machines

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US2031951A (en) * 1932-02-25 1936-02-25 Bell Telephone Labor Inc Burglar alarm system
US2071933A (en) * 1931-02-28 1937-02-23 Rca Corp Alarm system
US2400309A (en) * 1941-10-31 1946-05-14 Baldwin Co Oscillation generator
US2745089A (en) * 1954-01-19 1956-05-08 Isaac Ergas Burglar alarm and like warning systems
US2985018A (en) * 1956-10-22 1961-05-23 North American Aviation Inc Vibration wave distance measuring device
US3047850A (en) * 1959-08-12 1962-07-31 Mosler Res Products Inc Sonic space alarm
US3061829A (en) * 1959-12-14 1962-10-30 Diebold Inc Sonic alarm system
US3065455A (en) * 1958-10-07 1962-11-20 Wilfred Roth Detection apparatus
US3467804A (en) * 1966-01-03 1969-09-16 Microtherm Ltd Detection apparatus
US3569924A (en) * 1969-03-19 1971-03-09 Dexter Mfg Co Ultrasonic detection system
US3721972A (en) * 1972-02-22 1973-03-20 Seabord Electric Ultrasonic burglar alarm system
US3725888A (en) * 1971-04-05 1973-04-03 Pyrotector Inc Detector system

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2071933A (en) * 1931-02-28 1937-02-23 Rca Corp Alarm system
US2031951A (en) * 1932-02-25 1936-02-25 Bell Telephone Labor Inc Burglar alarm system
US2400309A (en) * 1941-10-31 1946-05-14 Baldwin Co Oscillation generator
US2745089A (en) * 1954-01-19 1956-05-08 Isaac Ergas Burglar alarm and like warning systems
US2985018A (en) * 1956-10-22 1961-05-23 North American Aviation Inc Vibration wave distance measuring device
US3065455A (en) * 1958-10-07 1962-11-20 Wilfred Roth Detection apparatus
US3047850A (en) * 1959-08-12 1962-07-31 Mosler Res Products Inc Sonic space alarm
US3061829A (en) * 1959-12-14 1962-10-30 Diebold Inc Sonic alarm system
US3467804A (en) * 1966-01-03 1969-09-16 Microtherm Ltd Detection apparatus
US3569924A (en) * 1969-03-19 1971-03-09 Dexter Mfg Co Ultrasonic detection system
US3725888A (en) * 1971-04-05 1973-04-03 Pyrotector Inc Detector system
US3721972A (en) * 1972-02-22 1973-03-20 Seabord Electric Ultrasonic burglar alarm system

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4229811A (en) * 1978-11-09 1980-10-21 General Electric Company Intrusion detection method and apparatus
US4260980A (en) * 1979-04-30 1981-04-07 Bates Mitchell G Blind spot detector for vehicles
US4853690A (en) * 1986-04-03 1989-08-01 Richard Hirschmann Radiotechnisches Werk Security alarm process and apparatus
EP0286897A1 (de) * 1987-04-09 1988-10-19 Cerberus Ag Verfahren und Vorrichtung zur Überwachung von geschlossenen Räumen
US5266905A (en) * 1992-05-29 1993-11-30 Audio Research Corporation Audio amplifier with amplified feedback
EP0909960A3 (de) * 1997-09-16 1999-05-19 f+g megamos Sicherheitselektronik GmbH Ultraschall-Überwachungseinrichtung zum Überwachen eines kfz-Innenraumes
EP0916969A3 (de) * 1997-11-11 1999-11-03 GRUNDIG Aktiengesellschaft Autoradioalarmanlage
US20080224863A1 (en) * 2005-10-07 2008-09-18 Harry Bachmann Method for Monitoring a Room and an Apparatus For Carrying Out the Method
US20110141283A1 (en) * 2009-12-14 2011-06-16 Electronics And Telecommunications Research Institute Security system and method using measurement of acoustic field variation
US8797407B2 (en) * 2009-12-14 2014-08-05 Electronics And Telecommunications Research Institute Security system and method using measurement of acoustic field variation
US10741037B2 (en) * 2018-05-16 2020-08-11 Avaya Inc. Method and system for detecting inaudible sounds

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GB1420043A (en) 1976-01-07
DE2237613A1 (de) 1974-03-07
FR2195017A1 (enrdf_load_html_response) 1974-03-01
BR7305723D0 (pt) 1974-08-29
IT991881B (it) 1975-08-30
DE2237613B2 (enrdf_load_html_response) 1974-10-17
JPS4980896A (enrdf_load_html_response) 1974-08-05
DE2237613C3 (de) 1975-05-28
FR2195017B3 (enrdf_load_html_response) 1976-07-09
ZA734591B (en) 1974-11-27
HU167448B (enrdf_load_html_response) 1975-10-28

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