WO1998038833A1 - Voice recording prevention system - Google Patents

Voice recording prevention system Download PDF

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Publication number
WO1998038833A1
WO1998038833A1 PCT/IL1998/000100 IL9800100W WO9838833A1 WO 1998038833 A1 WO1998038833 A1 WO 1998038833A1 IL 9800100 W IL9800100 W IL 9800100W WO 9838833 A1 WO9838833 A1 WO 9838833A1
Authority
WO
WIPO (PCT)
Prior art keywords
frequency
microphone
signal
signals
20khz
Prior art date
Application number
PCT/IL1998/000100
Other languages
French (fr)
Inventor
Daniel Adir
Eli Zohar
Dror Dvir
Original Assignee
Daniel Adir
Eli Zohar
Dror Dvir
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 Daniel Adir, Eli Zohar, Dror Dvir filed Critical Daniel Adir
Priority to AU61128/98A priority Critical patent/AU6112898A/en
Publication of WO1998038833A1 publication Critical patent/WO1998038833A1/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/02—Circuits for transducers, loudspeakers or microphones for preventing acoustic reaction, i.e. acoustic oscillatory feedback
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/1752—Masking
    • G10K11/1754—Speech masking
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/02—Synthesis of acoustic waves
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/40—Jamming having variable characteristics
    • H04K3/42—Jamming having variable characteristics characterized by the control of the jamming frequency or wavelength
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/80—Jamming or countermeasure characterized by its function
    • H04K3/82—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection
    • H04K3/825—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection by jamming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K2203/00—Jamming of communication; Countermeasures
    • H04K2203/10—Jamming or countermeasure used for a particular application
    • H04K2203/12—Jamming or countermeasure used for a particular application for acoustic communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/40—Jamming having variable characteristics
    • H04K3/43—Jamming having variable characteristics characterized by the control of the jamming power, signal-to-noise ratio or geographic coverage area

Abstract

Two ultrasonic signals (12, 16), one of them at a fixed frequency (16), and the other (12) at a nearby but varying frequency are acoustically radiated (14) into a space and nonlinearly interact at a microphone diaphragm to generate a masking sound in the microphone's output.

Description

VOICE RECORDING PREVENTION SYSTEM
The invention relates to a system for the prevention of voice recording or voice interception during meetings and of discussions in the vicinity of such system.
The system is based on the finding that when two Ultra Sonic signals, from independent sources, are mixed in free space or at the input of a microphone (which is a nonlinear component), there results a major resultant signal which is the difference between the original signal and that of the mixed signals.
If the difference between the signals has a frequency that is within the audio frequency band, and its level is high enough, it will garble any voice signal that will appear at the input of the microphone.
The system consists of two or more channels of Ultra Sonic sources: One is at a fixed frequency and the other's frequency varies continuously around the fixed frequency at a deviation smaller than 3 KHz, or both are of varying frequencies in the range of 0 to 3KHz.
Each noise source is amplified by a maximum efficiency amplifier, in order to reduce the power output required to mask the voices in the vicinity of the microphone.
A set of piezo-electric loudspeakers is connected to the output of the amplifiers. Again, the advantage of these loudspeakers is their efficiency.
The system is aimed to operate in meeting rooms and in free space in the vicinity of the talking persons. Power outputs for each use will be optimized to enable minimum power consumption, and in the case of free space use, to enable the unit to be self-sufficient and such that it can be carried in the bearer's brief case or coat. FIELD OF INVENTION
The invention relates to an apparatus which will prevent a tape recorder, or any other recording/bugging apparatus, from recording a conversation which takes place in the vicinity of the apparatus. It also prevents the*»nterception of the conversation by any party, by electronic means (microphone).
PRIOR ART
Noise generating apparatus, which generates noise at an audible frequency band are generally used. The noise generated by such apparatus is audible to the persons in its vicinity, thus, revealing the use of such an apparatus and it also causes irritation.
SUMMARY
The voice recording prevention system of the invention is aimed at preventing recordings of discussions during meetings in the vicinity of the unit's bearer.
The system is based on the idea that two or more Ultra Sonic signals from independent sources, will be mixed in free space or at the input of a microphone (which is a nonlinear component) and a major resultant signal is the difference between the original signal.
If the difference between the signals is within the audio frequency band, and its level is high enough, it will garble any voice signal that will appear at the input of the microphone.
The system consists of two or more channels of Ultra Sonic sources. One is at fixed frequency and the other's frequency varies continuously around the fixed frequency at a deviation smaller than 3 KHz. Each ultra-sonic energy source is amplified by a maximum efficiency amplifier, in order to reduce the power output required to overcome the voices in the vicinity of the microphone.
A set of piezo-electric loudspeakers is connected to the output of the amplifiers, the advantage of these being their efficiency.
The system can be operated in rooms, meeting rooms and in free space, at the vicinity of the talking persons. Power outputs for each use will be optimized to enable minimum power consumption and in cases of free space usage, to enable the unit to be self sufficient and carried in the bearer's brief case, or coat.
The novel system for preventing voice recording comprises two or more sources of ultiasonic sonic signals, in a certain frequency range and of a certain intensity. One of the frequencies can be a fixed one and the second a varying one, or both may be variable.
The signals are mixed either in free space or at the input of the microphone used for recording (which is a non-linear component) resulting in a signal which is the difference between the original signals. When this difference is in the audio frequency band, and it is of adequate intensity, such signal will mask voice signals at the input of the microphone.
Essentially the novel device comprises two or more sources of ultra-sonic waves. When one has a constant frequency, the frequency of the other source varies around this frequency at a deviation which is generally less than 3 KHz.
The following Example is illustrative only and is not to be construed in any limitative sense. A typical device is operated at an ultra sonic frequency in the 20 KHz to 100 KHz band at a power output of about 50W to 200W for room applications; of 10W to 50W for portable devices and at about 100W to about 500W for large halls.
The bandwidth used is generally up to 10 KHz.
The resulting signal which appears at the entrance of the recording microphone is a combination of the two ultra sound signals, each of them being of the type A-cos 0 t, where A is the amplitude of the signal, 0 is the frequency and t is the time.
When these are mixed in an uniiπear element, such as a microphone, there results a sum of the two signals, their difference, multiples of the frequency and harmonics of same.
As shown in the enclosed figure, which is a schematical block diagram of a system of the invention, such system comprises in combination: A noise source 11 in the 0.3 to 3.4 KHz band, which is frequency modulated and passed to a VCO, 12, with FO = 19.5 KHz Δ F= 4 KHz and to a Power amplifier 13, of 70 W which is connected with a LP 14 of about 4Ω.
There is further provided a switching Power supply 15 of 24 V, 5A, connected to the noise generator 11 and to 20 KHz oscillator 16 which provides the input of 70 W power amplifier 16, connected to another 4 Ω LP 17.

Claims

1. A system for preventing voice recordings in closed and open spaces which comprises two generators of ultra sonic signals with either one of them being at a fixed frequency and the other at a varying one, resulting in a signal which prevents voice transmission by a microphone.
2. A system according to Claim 1 , where the fixed frequency is in the range between about 20KHz to about 10.00mhz.
3. A system according to Claim 1 or 2, where the vaiiable frequency is in the tange of from about 20KHz to about 1000KHz.
4. A system according to any of Claims 1 to 3, where the intensity of the signal is about 200w for indoor use, about 50w for portable systems, and about 500w for large rooms.
5. A system according to Claim 1 , where the two or more generators of varying ultrasonic signals are used, the frequencies of which are combined, and where each of these is in the 20KHz to 1000 MHz range, and where the variation in frequency is 0 to 3KHz.
PCT/IL1998/000100 1997-03-02 1998-03-01 Voice recording prevention system WO1998038833A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU61128/98A AU6112898A (en) 1997-03-02 1998-03-01 Voice recording prevention system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL120355 1997-03-02
IL12035597A IL120355A0 (en) 1997-03-02 1997-03-02 Voice recording prevention system

Publications (1)

Publication Number Publication Date
WO1998038833A1 true WO1998038833A1 (en) 1998-09-03

Family

ID=11069874

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IL1998/000100 WO1998038833A1 (en) 1997-03-02 1998-03-01 Voice recording prevention system

Country Status (3)

Country Link
AU (1) AU6112898A (en)
IL (1) IL120355A0 (en)
WO (1) WO1998038833A1 (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105006232A (en) * 2015-03-03 2015-10-28 西北工业大学 Ultrasonic eavesdropping-resistant and secret-recording-resistant device and eavesdropping-resistant and secret-recording-resistant method using same
CN105047191A (en) * 2015-03-03 2015-11-11 西北工业大学 Ultrasonic active sound attenuation anti-eavesdrop and anti-wiretapping device, and anti-eavesdrop and anti-wiretapping method using the device
WO2016001716A1 (en) * 2014-07-02 2016-01-07 Armoni Hanan Method and apparatus for blocking microphones
US20190122691A1 (en) * 2017-10-20 2019-04-25 The Board Of Trustees Of The University Of Illinois Causing microphones to detect inaudible sounds and defense against inaudible attacks
US10805721B2 (en) * 2018-03-05 2020-10-13 Electronics And Telecommunications Research Institute Apparatus and method for preventing recording of electronic devices
WO2022128461A1 (en) * 2020-12-16 2022-06-23 Audi Ag Method for preventing a voice from being intercepted

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1616639A (en) * 1921-06-03 1927-02-08 Western Electric Co High-frequency sound-transmission system
US1951669A (en) * 1931-07-17 1934-03-20 Ramsey George Method and apparatus for producing sound
US2461344A (en) * 1945-01-29 1949-02-08 Rca Corp Signal transmission and receiving apparatus
US3398810A (en) * 1967-05-24 1968-08-27 William T. Clark Locally audible sound system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1616639A (en) * 1921-06-03 1927-02-08 Western Electric Co High-frequency sound-transmission system
US1951669A (en) * 1931-07-17 1934-03-20 Ramsey George Method and apparatus for producing sound
US2461344A (en) * 1945-01-29 1949-02-08 Rca Corp Signal transmission and receiving apparatus
US3398810A (en) * 1967-05-24 1968-08-27 William T. Clark Locally audible sound system

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016001716A1 (en) * 2014-07-02 2016-01-07 Armoni Hanan Method and apparatus for blocking microphones
CN105006232A (en) * 2015-03-03 2015-10-28 西北工业大学 Ultrasonic eavesdropping-resistant and secret-recording-resistant device and eavesdropping-resistant and secret-recording-resistant method using same
CN105047191A (en) * 2015-03-03 2015-11-11 西北工业大学 Ultrasonic active sound attenuation anti-eavesdrop and anti-wiretapping device, and anti-eavesdrop and anti-wiretapping method using the device
US20190122691A1 (en) * 2017-10-20 2019-04-25 The Board Of Trustees Of The University Of Illinois Causing microphones to detect inaudible sounds and defense against inaudible attacks
US10672416B2 (en) * 2017-10-20 2020-06-02 Board Of Trustees Of The University Of Illinois Causing microphones to detect inaudible sounds and defense against inaudible attacks
US11264047B2 (en) 2017-10-20 2022-03-01 Board Of Trustees Of The University Of Illinois Causing a voice enabled device to defend against inaudible signal attacks
US10805721B2 (en) * 2018-03-05 2020-10-13 Electronics And Telecommunications Research Institute Apparatus and method for preventing recording of electronic devices
WO2022128461A1 (en) * 2020-12-16 2022-06-23 Audi Ag Method for preventing a voice from being intercepted

Also Published As

Publication number Publication date
AU6112898A (en) 1998-09-18
IL120355A0 (en) 1997-07-13

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