WO2016001716A1

WO2016001716A1 - Method and apparatus for blocking microphones

Info

Publication number: WO2016001716A1
Application number: PCT/IB2014/062789
Authority: WO
Inventors: Hanan ARMONI; Saar SHLAPOBERSKY
Original assignee: Armoni Hanan; Shlapobersky Saar
Priority date: 2014-07-02
Filing date: 2014-07-02
Publication date: 2016-01-07

Abstract

The invention relates to a method for blocking a microphone (13) by overlaying sound waves (10, 11) in an area of overlap (12), wherein a first acoustic transmitter (1) emits a first sound wave (10), and at the same time a second acoustic transmitter (2) emits a second sound wave (11), wherein the first sound wave (10) has a fundamental at a first frequency, and the second sound wave (11) has a fundamental at a different, second frequency, wherein the directions of emission of the first sound wave (10) and the second sound wave (11) are substantially parallel to one another. The invention additionally relates to apparatuses for carrying out such methods.

Description

Method and device for blocking microphones

The invention relates to a method and apparatus for blocking microphones by superimposing sound waves.

The prior art discloses electromagnetic jammers (so-called signal jammers, also known as cellphone blockers) which are used to operate within certain local areas, for example in prisons,

Courthouses, but also schools, to make the use of mobile phones impossible. These jammers work in the frequency domain and affect the electromagnetic signal receiver of the mobile phone by sending

electromagnetic radiation such that the mobile phone is no longer able to receive or send signals.

However, mobile phones can still make acoustic recordings through the built-in microphone. Furthermore, of course, all purely acoustic recording devices, such as in particular dictation devices, smartphones with

Sound recorder or the like, not affected by electromagnetic jammers.

For situations in need of confidentiality, it is just desirable to prevent such acoustic recordings. For this purpose, known from the prior art, various methods based on acoustic

To emit interference signals that overlap the recorded conversation and thus mutilate or obscure the recording. Similar methods are also used to create a quiet zone within certain local areas. For this purpose, the ambient noise is picked up by microphones, and a correspondingly adapted negative signal is transmitted in a directional manner in this area. Numerous methods and devices for generating directional sound waves are also known from the military sector in order to achieve an acoustic effect in a defined local area.

However, all of the prior art methods use audible signals that are audible to the user and at least somewhat disturbing. This applies in particular to acoustic noise generators or "microphones / audio jammers", as they are commercially available in many cases, and inconspicuous use of such devices is virtually impossible, for which reason they are

Method is not suitable to block the microphones of electric recording devices inconspicuously and without disturbing the conversations in the impacted area such that a recording function is made impossible.

The object of the invention is therefore to provide an apparatus and a method for the acoustic interference of electric microphones, which works as inconspicuously as possible, but robust and reliable and can be used without causing a stir among the users.

According to the invention, the solution to this and other problems is that a first acoustic wave emits a first sound wave through a first acoustic transmitter, and

at the same time by a second acoustic transmitter, a second sound wave

is radiated, wherein the first sound wave is a fundamental with a first frequency, and the second sound wave is a fundamental with a

having different second frequency, wherein the emission directions of the first sound wave and the second sound wave are substantially parallel to each other.

According to the invention, provision can be made, in particular, for the first frequency and the second frequency to lie in a frequency range which is not audible to humans.

By the two sound waves are emitted parallel to each other and

Have fundamental vibrations whose frequencies differ only slightly from each other, takes place within a local overlay region of the two sound waves, an interference pattern in the form of a standing wave whose frequency corresponds to the absolute value of the difference of the first and second frequencies. By appropriate choice of the two fundamental frequencies, the interference pattern can be formed within a certain range such that the standing sound wave has a frequency suitable to block the electric microphone. The standing sound wave can have a low frequency, for example in the range of 200Hz to 1500Hz. This can be a frequency that is audible to humans, in particular in the range of 60QHz to 1000Hz.

However, it has surprisingly been found that when choosing certain first and second frequencies forms a standing wave that is not audible on the one hand for humans, but on the other hand still the recording function of electric microphones, especially condenser microphones blocked.

This surprising effect is attributed to the fact that a condenser microphone always has a non-linear resonance region in front of the sound-absorbing, movable membrane, which represents the capacitor plate: The standing wave is suitable for inducing vibrations within this resonance range, which blocks the movable capacitor plate in such microphones thus makes a recording function impossible. The recording function in electret microphones may also be blocked by the standing wave of the

electronic recording amplifier (usually a field effect transistor) is driven into saturation and thus can not record any further signals.

To achieve this effect, the standing wave can also be used in one for the

People are inaudible frequency range, since the standing sound wave is generated by the nonlinearity of the air in the resonance range of the microphone and the nonlinearity of the diaphragm. It has been found that the first and second frequencies can particularly advantageously have values in the range from 20 kHz to 50 kHz, preferably 35 kHz to 45 kHz, particularly preferably 40 kHz, in order to bring about this effect. In particular, the first frequency can have a value of 39.5kHz, and the second

Frequency have a value of 40.5kHz. According to the invention, the absolute value of the difference of the first and second

Frequency at least 10 Hz. According to the invention, however, the absolute value of the difference between the first and second frequencies may also be 10 Hz to 15 kHz, preferably 10 Hz to 1500 Hz, particularly preferably 200 Hz to 1500 Hz. This is due to the fact that it has been found that different

Recording devices can be blocked by different frequency ranges. Thus, a conversation on a mobile phone can be particularly effective through a

Difference frequency can be blocked in the range of 10 Hz to 1500 Hz. On the other hand, an audio recording device, such as a dictaphone, but also a smartphone with

Audio recorder, particularly effectively be blocked by a difference frequency in the range of 10 Hz to 15 kHz.

According to the invention, provision can be made, in particular, for the first sound wave and / or the second sound wave to be generated by first generating electrical signals by electrical signal generators, which are conducted via electrical amplifiers to loudspeakers which generate the actual sound waves.

According to the invention, it may further be provided that at least one of the electrical signals, before amplification, is modulated with an electrical random signal,

preferably frequency modulated, is. However, the random signal may also have a time constant frequency in the range of 10 Hz to 15 kHz, preferably in the range of 10 Hz to 1500 Hz. It can also be provided that the amplitude and / or the frequency of the electrical random signal change over time. The random signal may also include a fundamental harmonic and at least one harmonic. The electrical signals and / or the random signal may in particular be sinusoidal signals, square-wave signals or triangular signals.

By modulating one of the electrical signals with the random signal, there is the effect that the absolute value of the difference of the two emitted

Sound waves constantly changed over time, and thus the frequency of the standing wave in the overlapping area is not constant. This ensures that the inventive method is effective for condenser microphones with a wide variety of resonance chambers. The overlapping area achievable with the standing wave is strongly dependent on the spatial orientation of the loudspeakers to one another. For this reason, the invention provides that the two transmitters are arranged at a distance from one another. This distance can be 0cm to 60cm, preferably 25cm to 45cm, most preferably 35cm. This ensures that the

inventive overlay effect in a very specific local

Overlap area is achieved.

Preferably, the distance can be chosen so that the effect of the invention at a distance of about 7m from the speakers has its strongest expression, the spatial extent of the Überiappungsbereichs in the horizontal direction can be about 2m in this distance.

According to the invention, it can be provided that the sound waves have a sound pressure level of 120 dB SPL to 140 dB SPL, preferably 130 dB SPL, at a distance of 1 m from the respective loudspeaker. This ensures that the standing wave in the overlap region has a sound pressure level in the range of 70dB SPL. In particular, it can be provided that the sound pressure level of the standing wave is about 50 dB lower than the sound pressure level of the generated sound waves.

The invention further extends to a device for blocking a

Microphones by superposition of sound waves in an overlap region, wherein a first acoustic transmitter for emitting a first sound wave and a second acoustic transmitter for simultaneously emitting a second sound wave are provided, wherein the first sound wave fundamental with a first frequency, and the second sound wave fundamental vibration with a

having different second frequency.

The transmitters can be arranged such that the emission directions of the first sound wave and the second sound wave are substantially parallel to one another. The absolute value of the difference of the first and second frequencies may preferably be at least 10 Hz. According to the invention, the absolute value of the difference of the first and second

Frequency in the range of 10 Hz to 15 kHz, preferably in the range of 10 Hz to 1500 Hz.

Such a device is for realizing the above-described

method according to the invention and has the advantages described above.

To generate the first sound wave and / or the second sound wave, electrical signal generators can be provided which generate electrical signals which are conducted via amplifiers to loudspeakers. Furthermore, at least one modulator or mixer and an electrical random signal generator may be provided to modulate at least one of the electrical signals with an electrical random signal, preferably using frequency modulation, the frequency of the random signal being in the range of 10 Hz to 15 kHz, preferably in the range of 10 Hz to 500 Hz varies.

The random signal generator may be designed to generate a random signal whose amplitude changes over time and / or whose frequency changes over time. It can also be provided that the random signal is a harmonic

Fundamental oscillation and at least one harmonic harmonic.

The two transmitters can be arranged at a distance from one another which is 10 cm to 60 cm, preferably 25 cm to 45 cm, particularly preferably 35 cm. The first frequency and / or the second frequency may be 20kHz to 50kHz, preferably 35kHz to 45kHz, more preferably 40kHz. In particular, it may be provided that the first frequency has a value of 39.5 kHz and the second frequency has a value of 40.5 kHz.

The amplifiers and the speakers can be designed such that the

Sound waves at a distance of 1 m from the speaker have a sound pressure level of 120dB SPL to 140dB SPL, preferably 130dB SPL. The loudspeakers can have a multiplicity of matrix-like arranged

Standard speakers include, which are arranged on one or more speaker plates in a plane or along a curve.

The loudspeakers can also be arranged on a flexible printed circuit board, which in particular can be curved, particularly preferably convexly curved.

According to the invention, a plurality of loudspeakers of a first loudspeaker group and a plurality of loudspeakers of a second loudspeaker group can also be arranged on a preferably curved, particularly preferably convexly curved printed circuit board, the loudspeakers of the first loudspeaker group emitting the first sound wave, and the loudspeakers of the second loudspeaker group respectively the second sound wave Radiating, wherein to adjust the achievable sound pressure level speakers of the first and second speaker group are each activated in pairs.

The invention further extends to a device, in particular a scanner, for blocking a microphone, comprising a device according to the invention, wherein a first transmission range and a second, spatially separate second transmission range are provided, wherein in each of the first and second transmission range an electrical signal generator, an amplifier, as well as a plurality of loudspeakers are provided, wherein in each case a loudspeaker of the first transmission range is assigned to a loudspeaker of the second transmission range, and the loudspeakers of a transmission range are offset from each other by a defined angle, wherein associated loudspeakers have identical emission directions, and in each of two transmission areas a multiplexer is provided to activate associated speakers simultaneously.

According to the invention, it may be provided that the loudspeakers of the first

Transmitting range by 10 ° to 15 °, preferably 12 °, are arranged offset to the speakers of the second transmission range to the respective generated

Extend overlap area to an expanded environment. According to the invention, the loudspeakers of the first transmission range and the

Loudspeaker of the second transmission range to be arranged on at least one flexible, preferably curved, more preferably convex curved circuit board.

According to the invention, it is possible for six each to be arranged offset by 12 ° in the first transmission range and in the second transmission range

Loudspeakers are arranged. The scanner can be designed in particular as a portable unit. The scanner can also be designed flat and executed, for example in the form of a wall paneling or an image.

The invention further extends to a method for operating a

Scanners according to the invention, wherein the associated loudspeakers are activated by the multiplexer in a defined sequence, preferably continuously, for a defined, preferably identical, period of time, preferably in the range of 7 to 15 seconds.

Further features of the invention will become apparent from the claims, the

Embodiments and the figures.

The invention will now be explained with reference to exemplary embodiments.

Fig. 1 shows a schematic representation of an embodiment of a

Device according to the invention for blocking an electric microphone;

Fig. 2 shows a schematic representation of the generated signal spectrum;

3 shows a schematic representation of an embodiment of a

inventive scanner;

FIGS. 4a-4b show schematic representations of embodiments

loudspeaker plates according to the invention;

Fig. 5a-5d shows a schematic representation of an embodiment of a

inventive scanner;

Fig. 6 shows a schematic representation of the preferred arrangement of several inventive scanner in a room;

Fig. 7 shows a schematic representation of the arrangement of several

Standard speaker on a speaker plate according to the invention.

Fig. 1 shows a schematic representation of a first embodiment of a device according to the invention. This comprises a first acoustic transmitter 1 and a second acoustic transmitter 2, which are arranged side by side at a distance 19 which is about 35 cm. The first acoustic transmitter 1 comprises a first signal generator 3, an amplifier 5 and a first loudspeaker 6. The second acoustic transmitter 2 comprises a second signal generator 4, an amplifier 5 and a second loudspeaker 7. The first signal generator 3 generates an electrical signal 21 a frequency f1 of about 40kHz. The second signal generator 4 generates an electrical signal 22 having a frequency f2 of about 40 kHz.

The second acoustic transmitter 2 further includes an electrical

Random signal generator 8. The random generator 8 generates a random signal 20 in

Frequency range from 10Hz to 1500Hz. This random signal is modulated onto the signal f2 generated by the second signal generator 4 by frequency modulation. Due to the modulation arise two symmetrical to the carrier frequency f2

Frequencies at a distance of the frequency of the random signal, whereby a modulated signal fm is generated. The frequency f1 generated by the first signal generator and the frequency fm generated by the second signal generator and the mixer differ by a frequency range of about 10 Hz to 1500 Hz. These signals are supplied to amplifiers 5 and speakers 6, 7 to produce sound waves.

The sound waves 10 and 11 emitted by the two loudspeakers 5 are superimposed in space, and an overlap region 12 is created within which a sum signal f1 + fm and a difference signal f1-fm are produced. The microphone 13 to be blocked is located within this overlapping area 12.

Fig. 2 shows a schematic representation of the spectrum of the generated sound waves. The first sound wave 10 has its fundamental at the frequency f1, and the second sound wave 1 1 has its fundamental at the frequency fm. The two sound waves differ by a frequency dF. Due to the overlay is in the

Overlap area a sum signal f1 + fm (not shown) and a

Difference signal fm-f1 formed. This difference signal 14 is located at a much lower frequency within the indicated by dashed lines, for the

People audible spectral range.

By constantly changing the frequency fm over time by the variable-frequency random signal, the difference signal 14 also constantly moves back and forth within the range indicated by the dashed line over time, whereby the formation of the standing wave and the blocking of the resonance space for different electrical Microphone types is achieved.

FIG. 3 shows a schematic representation of an embodiment according to the invention of a scanner for blocking electrical microphones 13 within a scanner

extended area. The scanner 15 comprises a first acoustic transmitter 1 for directional radiation of a first sound wave 10 and a second acoustic transmitter 2 for directional radiation of a second sound wave 1 1. The two

Sound waves 10, 1 1 overlap in an overlap region 12 and block a microphone 13 located there.

The first acoustic transmitter 1 comprises a signal generator 3, an amplifier 5 and six loudspeakers 6, 6a, 6b, 6c, 6d, 6e offset from each other at an angle. Only one of the six loudspeakers can be controlled by the signal generator 3. For this purpose, a, preferably electronically realized, multiplexer 16 is provided. The speakers 6, 6a, 6b, 6c, 6d, 6e are arranged side by side, but have a radiation direction offset by 12 ° in each case. This ensures that in the first transmission range 23, an angular range of up to 60 ° can be achieved.

The second acoustic transmitter 1 likewise comprises a signal generator 4, an amplifier 5 and six mutually offset by an angle

Loudspeaker 7, 7a, 7b, 7c, 7d, 7e. There is provided a random signal generator 8 and a mixer 9 for varying the difference signal.

As with the first acoustic transmitter 1, only one of the six loudspeakers can always be controlled by the signal generator 4 in the case of the second acoustic transmitter 2. For this purpose, a, preferably electronically realized, multiplexer 16 is provided. The speakers 7, 7a, 7b, 7c, 7d, 7e are arranged directly next to one another, but have a radiation direction offset by 12 ° in each case. This ensures that in the second transmission range 24, an angular range of up to 60 ° can be achieved.

Figs. 4a-4b show schematic representations according to the invention

Embodiments of the speaker plate 27, on which the first speaker 6 or the second speaker 7 are arranged. The first speakers 6 are standard components that are connected in parallel to achieve the required sound pressure level of the ultrasonic waves. The speaker plate 27 is fixed to three spacers 25, wherein by adjusting fastening nuts on the spacers 25, the inclination of the speaker plate 27 is adjustable with respect to a support surface. 4b shows a further embodiment of the

Speaker plate 27, wherein only in certain areas of the speaker plate 27 first speaker 6 are arranged. However, the first speakers 6 are not arranged directly next to each other, but spaced from each other to the

to achieve desired propagation of the ultrasonic waves, and to achieve that adjusts the overlap area only at a certain distance.

5a-5d show schematic representations of an embodiment of a

Scanners 15 according to the invention analogous to the embodiment of FIG. 3 with an indicated cover 26 and a first sentence arranged behind it

Speakers 6, 6a, 6b, 6c, 6d, 6e and a set of second speakers 7, 7a, 7b, 7c, 7d, 7e. The control of the speakers is carried out as in the embodiment of FIG. 3rd However, the loudspeakers 6, 6a, 6b, 6c, 6d, 6e are arranged in this exemplary embodiment in such a way that the respective activated loudspeaker pairs do not act directly

lie next to each other, but are arranged at a distance to each other.

This has the advantage that a further spatial area can be covered with the sound waves, and the overlapping area of the sound waves is set only at a distance of about 2.5 m from the scanner 15. The first and second

Loudspeakers are activated in pairs, so first the loudspeakers 6 and 7 are activated, then the loudspeakers 6a and 7a, and so on.

As shown in the sectional views Fig. 5b-5d, the associated pairs of speakers each have the same emission direction. Unrelated speaker pairs have a radiation direction offset by 12 ° each. This ensures that an angular range of up to 60 ° can be achieved, whereby an advantageous form factor of the scanner 15 is achieved by the special, rectangular arrangement of the speaker plates 27 with the first and second speakers.

The inclination of the speaker plates 27 with respect to the support plate 29 can be done by tightening or loosening the spacer 25, which are formed by an adjustable screw with coil spring. The control of the first and second speakers is not shown in the schematic representation for reasons of clarity.

6 shows a schematic representation of the arrangement of two scanners 15a, 15b in a room, for example a conference room. The first scanner 15a emits a first sound wave 10a and a second sound wave 11a, which overlap at a distance of about 2 m from the scanner 15a and form a superposition region 12a within which microphones are blocked. The second scanner 15b also emits a first sound wave 10b and a second sound wave 1b, which overlap at a distance of about 2 m from the scanner 15b and form a superposition region 12b within which microphones are blocked. The scanners 15a, 15b each cover an angular range of about 60 °, within which the

Overlap areas 12a, 12b are continuously moved. By the

Arrangement of the two scanners 15a, 15b in opposite corners of the room is achieved that, despite an obstacle 28, the entire space can be covered. FIG. 7 shows a further embodiment of a device according to the invention, wherein standard loudspeakers 6, 6a, 6b, 6c of a first loudspeaker group and

Standard speakers 7, 7a, 7b, 7c, 7d a second group of speakers on a convex curved circuit board 27, which is arranged on a support plate 29, are arranged like a matrix. The speakers 6, 6a, 6b, 6c of the first

Loudspeaker group radiate respectively the first sound wave 10, and the loudspeakers 7, 7a, 7b, 7c, 7d of the second loudspeaker group radiate respectively the second sound wave 1 1 from. Due to the curved printed circuit board and the special arrangement of the speakers, a large spatial area is covered. To adjust the sound pressure level, the loudspeakers of the first and second loudspeaker groups can be activated in pairs. If a low sound pressure level is sufficient, only the loudspeakers A and A 'are activated; if higher sound pressure levels are to be achieved, the speaker pairs B-B ', C-C, and finally D-D' are connected. When all speakers are activated, it will be at a distance of 3m

Sound pressure level of at least 130dB SPL achieved, with the horizontal coverage about 1, 5m and the vertical cover is about 60cm.

The invention is not limited to the present embodiments, but extends to all embodiments within the scope of the following

Claims.

LIST OF REFERENCE NUMBERS

1 first acoustic transmitter

2 Second acoustic transmitter

3 first signal generator

4 second signal generator

5 amplifiers

6, 6a, 6b, 6c, 6d, 6e First speaker

7, 7a, 7b, 7c, 7d, 7e Second speaker

8 random signal generator

9 mixers

10, 10a, 10b First sound wave

1 1, 1 1 a, 11 b Second sound wave

12, 12a, 12b overlap area

13 microphone

14 difference signal

15, 15a, 15b scanner

16 multiplexers

17 First partial loudspeaker

18 second partial loudspeaker

19 distance

20 random signal

21 First electrical signal

22 Second electrical signal

23 First transmission area

24 Second transmission area

25 spacers

26 cover

27 speaker plate

28 obstacle

29 carrier plate

Claims

claims

1. A method for blocking a microphone (13) by superposition of

Sound waves (10, 11) in an overlap region (12), characterized

marked that

a. by a first acoustic transmitter (1) a first sound wave (10) is emitted, and simultaneously

b. by a second acoustic transmitter (2) a second sound wave (11) is emitted,

c. wherein the first sound wave (10) has a fundamental with a first frequency, and the second sound wave (11) has a fundamental with a different second frequency, wherein d. the emission directions of the first sound wave (10) and the second

Sound wave (11) are substantially parallel to each other.

2. The method according to claim 1, characterized in that the difference of the first frequency and the second frequency is at least 10 Hz.

3. The method according to claim 2, characterized in that the difference of the first frequency and second frequency 10Hz to 15kHz, preferably 10Hz to 1500Hz, more preferably 200Hz to 1500Hz.

4. The method according to any one of claims 1 to 3, characterized in that the first sound wave (10) and / or the second sound wave (11) are generated by electric signals generated by electrical signal generators (3, 4) (21, 22) via amplifiers (5) to loudspeakers (6, 7) are guided, wherein the electrical signals (21, 22) are preferably sinusoidal signals, square wave signals or triangular signals.

5. The method according to claim 4, characterized in that at least one of the electrical signals (21, 22) with an electrical random signal (20) is modulated, preferably frequency-modulated, wherein the frequency of the random signal (20) in the range of 10Hz to 15kHz, preferably varies in the range of 0Hz to 1500Hz.

6. The method according to any one of claims 1 to 5, characterized in that the two transmitters (1, 2) at a distance (19) are arranged to each other, wherein the distance is preferably 10cm to 60cm, more preferably 25cm to 45cm, in particular 35cm ,

7. The method according to any one of claims 1 to 6, characterized in that the first frequency and / or the second frequency 20kHz to 50kHz, preferably 35kHz to 45kHz, more preferably 40kHz.

8. The method according to any one of claims 1 to 7, characterized in that the sound waves (10, 11) are emitted with a sound pressure level of more than 115 dB, preferably 120dB to 140dB, more preferably 130dB.

9. Device for blocking a microphone (13) by superposition of sound waves (10, 11) in an overlap region (12), characterized

marked that

a. a first acoustic transmitter (1) for emitting a first sound wave (10) and

b. a second acoustic transmitter (2) are provided for the simultaneous emission of a second sound wave (11),

c. wherein the first sound wave (10) has a fundamental at a first frequency, and the second sound wave (11) has a fundamental at a different second frequency, wherein

d. the transmitters (1, 2) are arranged such that the emission directions of the first sound wave (10) and the second sound wave (11) are substantially parallel to each other.

10. The device according to claim 9, characterized in that the difference of the first frequency and the second frequency is at least 10 Hz.

11. The device according to claim 10, characterized in that the difference of the first frequency and second frequency in the range of 10 Hz to 15 kHz, preferably in the range of 10 Hz to 1500 Hz.

12. Device according to one of claims 9 to 11, characterized in that for generating the first sound wave (10) and / or the second sound wave (1) electrical signal generators (3, 4) are provided, the electrical signals (21, 22) generate, which via amplifiers (5) to speakers (6, 7) are performed.

13. Device according to one of claims 9 to 12, characterized in that at least one modulator or mixer (9) and an electrical

Random signal generator (8) is provided to modulate at least one of the electrical signals (21, 22) with an electrical random signal (20), preferably using frequency modulation, wherein the frequency of the random signal in the range of 10Hz to 15kHz, preferably in the range of 10Hz to 1500Hz varies.

14. Device according to one of claims 9 to 13, characterized in that the random signal generator (8) for generating a random signal (20) is executed,

a. whose amplitude changes over time, and / or

b. whose frequency changes over time, and / or

c. which comprises a fundamental and at least one harmonic.

15. Device according to one of claims 9 to 14, characterized in that the first frequency and / or the second frequency 20kHz to 60kHz,

preferably 35 kHz to 45 kHz, more preferably 40 kHz.

16. Device according to one of claims 12 to 15, characterized in that the amplifier (5) and the speakers (6, 7) are designed such that the sound waves (10, 1 1) with a sound pressure level of about 1 15dB, preferably 120dB to 140dB, more preferably 30dB are emitted.

17. Device according to one of claims 12 to 16, characterized in that the loudspeakers (6, 7) arranged a plurality of a matrix

Standard speakers include one or more

Speaker plates (27) are arranged in a plane or along a curve.

18. Device according to claim 17, characterized in that loudspeakers (6, 6a, 6b, 6c) of a first loudspeaker group and loudspeakers (7, 7a, 7b, 7c, 7d) of a second loudspeaker group on a preferably curved, particularly preferably convexly curved printed circuit board (27) are arranged like a die, wherein the speakers (6, 6a, 6b, 6c) of the first

Speaker group each emit the first sound wave (10), and the speakers (7, 7a, 7b, 7c, 7d) of the second group of speakers each emit the second sound wave (1 1), and to adjust the achievable sound pressure level speakers of the first and second speaker group respectively can be activated in pairs.

9. Device, in particular scanner (15), for blocking a microphone (13), comprising a device according to one of claims 9 to 18, characterized in that

a. that a first transmission range (23) and a second, spatially thereof

separate second transmission area (24) are provided,

b. wherein in each of the first and second transmission range an electrical

Signal generator (3, 4), an amplifier (5), and a plurality of loudspeakers (6, 6a, 6b, 6c, 6d, 6e; 7, 7a, 7b, 7c, 7d, 7e) are provided, wherein c. in each case a loudspeaker of the first transmission range (6, 6a, 6b, 6c, 6d, 6e) is associated with a loudspeaker of the second transmission range (7, 7a, 7b, 7c, 7d, 7e), and

d. the loudspeakers of a transmission range (23, 24) are offset relative to each other by a defined angle, preferably 10 ° to 15 °, particularly preferably 12 °, wherein

e. associated speakers have identical emission directions, f. and a multiplexer (16) is provided to each associated

Activate speakers at the same time.

20. The apparatus according to claim 19, characterized in that the speakers of the first transmission range (6, 6a, 6b, 6c, 6d, 6e) and the speakers of the second transmission range (7, 7a, 7b, 7c, 7d, 7e) on each other arranged separately loudspeaker plates (27) are arranged, wherein the

Lautsprecherp! Atten (27) of the first transmission range offset and spaced from the speaker plates of the second transmission range are arranged.

21. Device according to claim 19 or 20, characterized in that the

Speaker of the first transmission range (6, 6a, 6b, 6c, 6d, 6e) and the

Loudspeaker of the second transmission range (7, 7a, 7b, 7c, 7d, 7e) are arranged on at least one flexible, preferably curved, particularly preferably convexly curved printed circuit board.

22. A method for operating a device according to one of claims 19 to 21, characterized in that the associated loudspeakers by the multiplexer (16) in a defined sequence, preferably continuously, for a defined, preferably identical, time period, preferably in the range of 7 to 15 seconds, be activated.