RU2556272C2 - Vibratory noise unit for acoustic voice data leak channel - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device comprises electrical generator to develop noise signal connected to vibroexciter, inertial mass connected with vibroexciter. Vibroexciter is connected with the room noisy element. Note here that vibroexciter is pressed directly to said room noisy element while counterweight is pressed directly to vibroexciter, both being pressed by resilient clip to noisy element. Second end of resilient clip is secured at fixed or noisy element. Besides, said counterweight has limiting ledges to retain said vibroexciter. Noise signal generator is integrated with counterweight while the device is provided with the set of replaceable vibroexciter clips, counterweights and their fasteners.

EFFECT: simplified design and attachment, higher efficiency and reliability.

4 cl, 5 dwg, 1 tbl

Description

The invention relates to devices for creating artificial interference for noise vibration channels leakage of acoustic speech information.

As you know, such a leak is possible through the framing elements of the room (windows, walls, doors, heating and water pipes, floor, ceiling and other building structures), in which confidential negotiations and meetings are held. Under the influence of the acoustic field of human speech, vibration occurs in these structures (the so-called "dangerous signal"), which can spread over considerable distances. A special observation equipment allows you to remotely perceive this vibration and restore the original acoustic signal. The simplest device for interception through a vibration channel is a medical stethoscope. More complex - laser pullers - are able to carry out contactless removal from a distance of hundreds of meters.

To prevent leakage of acoustic information through the vibration channel, it is necessary to create artificial noise vibrations in building structures that block the “dangerous signal” in amplitude. Moreover, the excess of the noisy signal over the "dangerous signal" must be observed at all frequencies in the frequency range of human speech.

A typical circuit for the noise of a vibrational leakage channel comprises an electric noise interference generator connected to a vibration exciter that converts the noise electrical noise into vibration.

When noisy structural elements of the room (hereinafter referred to as noisy elements), it is necessary to take into account the differences in their susceptibility to acoustic effects at different frequencies and form the corresponding vibration spectrum.

For example, a heating battery is more susceptible to higher and less to lower frequencies of the speech range than window glass. In this case, both the battery and the glass are especially susceptible to frequencies below 500 Hz [7]. Concrete floors and brick walls according to the data given in [9, p.176, 177], are equally susceptible to acoustic effects in the entire frequency range.

Unfortunately, the theory of optimizing the operation of noise devices is currently underdeveloped.

So, according to the data of [9, p.176, 177], the operating systems of vibrational noise suppression have a deficit of the level of noise vibrations at frequencies below 500 Hz. In our opinion, this can be explained by the insufficiency of the inertial mass of vibration exciters and the imperfection of their fastening on a noisy element.

It is known that the accelerations acquired by bodies as a result of their interaction are inversely proportional to the masses of interacting bodies.

If the mass of the vibration exciter m _{1 is} much less than the moving mass of the noisy element m ₂ , then the acceleration of the noisy element a _{2 is} much less than the acceleration of the exciter a ₁ . In other words, the exciter vibrates, and the noisy wall (window, heating battery) remains in place.

With increasing frequency, the moving mass of the noisy element decreases, and vibration acceleration increases in proportion to the square of the frequency (with a fixed amplitude of vibrations), therefore, noise at low frequencies is a technical problem.

An “ideal” noise device should create vibrations in the noise element with a wide frequency spectrum, which has a rise at low frequencies. In addition, it should be possible to change the spectrum for the noise of various elements of the room.

Typically, high-power noise signal generators with deep frequency correction (by raising at the bottom of the spectrum) are used to solve this problem. But the use of such generators to correct the low efficiency of the vibration exciter is an expensive, low-efficiency solution.

Known devices that create noisy vibrations in the room's framing elements that carry traces of a "dangerous signal" - see, for example, US patents for inventions 4010324, 4098370, RF patents for utility models 21490, 27442, 30478, 49363, RF patent for invention 2408143.

US Pat. No. 4,010,324 [1] proposes a background sound masking device, but it is inconvenient for mass operational use.

US Pat. No. 4,098,370 [2] proposes a device for generating vibrating sound-masking signals in a room by powerful acoustic waves. However, such protection did not provide interference with the necessary amplitude-frequency characteristic.

In RF patent 21490 [3] a vibroacoustic interference emitter is proposed, in which the vibroacoustic signal shaper is made in the form of an electromagnetic vibrator having a permanent magnet, an induction coil, a moving core and a unit for influencing the room’s framing. The magnet and induction coil also perform the function of an inertial element. In this case, the mechanical impact unit is made in the form of an anchor rigidly attached to the frame of the room and connected by springs with a movable core. To equalize the frequency response of the noise signal, a parallel RC circuit is used at the input of the vibration exciter. The specified alignment is necessary due to the fact that the resistance of the induction coil increases with increasing frequency of exciting oscillations, as a result of which the amplitude of the vibrations decreases.

The described construction has a number of significant drawbacks. It is complex, has a low coefficient of utilization of the power of the noise generator, since the corrective circuit dissipates a significant part of the generator power. The disadvantage of the design of the device is that the rapid replacement of the vibration exciter is almost impossible. The patent does not indicate the method of fastening the emitter to the framing elements of the room, although practice shows that it significantly affects the characteristics of vibration noise.

Let's consider it in more detail. In most cases, noise suppression devices are installed on walls, windows, radiators and vibration is produced in horizontal directions, i.e. noise devices hang on the indicated elements of the frame of the premises, exciting vibrations in them. Usually they are attached to the wall with a screw or glue, and to the window - only with glue. However, the adhesive fastening on a vibrating object is short-lived and unreliable, it gradually collapses over time, noticeably changing the transmission of vibrations to a noisy room element.

The adhesive fastening of the device is especially often destroyed on the windows under the influence of sunlight, condensation and a sharp temperature difference. There are recommendations for fixing devices to window panes using photosensitive glue [8]. The manufacturer guarantees bonding reliability. However, when the glued devices fail, their replacement is impossible and you have to glue other devices nearby or change them together with the glass. Naturally, such a mount is of little use in conditions of operational (at the time of confidential negotiations) equipment of the premises with noise devices.

In the patent of the Russian Federation 27442 [4], a device for vibro-acoustic noise is proposed, in which several vibration exciters are used, each of which is powered by its own speech-like noise generator located next to the vibration exciter. Power to these noise signal generators is supplied from a common power source. This design allows you to choose the most suitable mode for each vibration exciter (it will be shown below that the inventive device allows you to provide a suitable mode of operation with the selection of inertial elements, which is less costly), and also eliminate the risk of removal of acoustic information (microphone effect) from the device’s power wires. The patent does not mention the inertial masses and also does not indicate the method of attaching the vibration exciter to the noisy elements of the room, which, as shown above, significantly affects the actual characteristics of the device.

Patent 49363 [5] proposes a noise suppression device comprising a vibration exciter comprising a piezoelectric element glued to a metal plate pressed around the circumference by an inertial mass. The metal plate is located on the masked element of the frame of the room and is attached to it by a protrusion in the center down for insertion into the noisy element. Such a device has a relatively low efficiency due to the intermediate transmission elements between the vibration exciter and the noise element, as well as between the vibration exciter and the inertial mass. At the same time, the operational replacement of the vibration exciter is practically excluded. The device is difficult to mount - for example, it cannot be used to noise the window. It can be used only stationary, only for walls, in rooms that are constantly equipped with noise devices.

RF patent 2408143 [6] is a noisy device with two noise sources - acoustic and vibration. They are excited from a single noise generator. The possibility of prompt replacement of vibration exciters is excluded. In this case, the electrovibration converter is rigidly fixed to the inner wall of the base of the noise source housing, and the leg of the noise source housing is screwed to the object of protection. The device can only be used to noise the walls. Another disadvantage of the device from the point of view of vibration noise is that the exciter does not have any inertial pressure from the side opposite to the object of protection. In addition, vibrations from the exciter to the noisy room element are transmitted not directly, but through several intermediate elements (case, membrane, leg), which noticeably reduce its power and distort the frequency response of the radiation. At the same time, conflicting requirements are imposed on the membrane: on the one hand, it must provide mechanical strength, i.e. be thick, but, on the other hand, must be flexible to transmit vibrations.

A brief review of modern devices of vibro-acoustic noise cancellation showed that they are not effective enough, especially in the field of low sound frequencies, there are no simple and reliable means of attaching them to different elements of the frame of the room. They are usually specific (i.e., suitable for use only for a particular element - a window, or a wall, or a heating pipe), in them the replacement of the vibration exciter is almost impossible. In addition, in none of the patents considered, the vibration exciter is not clamped directly between the noisy room element and the inertial element. Meanwhile, the intermediate structural elements weaken and distort the transmission of vibrations from the exciter to the noisy element. The inertial elements (inertial masses) in the considered patents are connected to the vibration exciter by a common housing attached to the noisy element of the room’s frame, and this common housing limits the increase in mass of the inertial element and dampens useful vibrations of the vibration exciter, that is, reduces the efficiency.

The above-mentioned inertial element, as established in [7], and will be confirmed below, significantly affects the efficiency of the device and its frequency response, especially in the low-frequency region,

Closest to the claimed (prototype of the invention) device according to the patent of the Russian Federation No. 49363 (IPC7 H01L 41/08, published November 10, 2005). Recall this: a piezoelectric transducer comprising a piezoceramic disk, a metal membrane and an inertial element, the metal membrane being made with a protrusion on the periphery, by means of which it is rigidly connected to the inertial element, from which it is covered by a dielectric layer and rigidly connected to the piezoelectric disk, and on the opposite side, the metal membrane in the central part has a protrusion for rigid attachment to the building structure.

As noted above, such a device has a relatively low efficiency, the operational replacement of the vibration exciter is practically excluded. The device is difficult in design and inconvenient to mount - for example, it cannot be used to noise the window. In addition, it can only be used permanently, only for walls, in rooms that are constantly equipped with devices.

The technical result, which the invention is directed to, is to increase the efficiency of the device of vibrational noise by increasing the coefficient of power transfer from the vibration exciter to the noisy element of the frame of the room, in other words - increasing the efficiency of the device;

Another objective of the invention is to simplify its design and create the possibility of rapid installation on various objects, including those previously not adapted for the special conservation of acoustic information. Moreover, embodiments of the device should allow combining the components in such a way that they correspond to the features of various typical objects.

The third objective of the invention is to increase reliability and maintainability due to a new method of attaching the device to a noisy element and the possibility of rapid replacement of the vibration exciter and inertial element.

These tasks are carried out by the fact that in the known device of vibrational noise channel leakage of acoustic speech information containing an electric noise signal generator connected to a vibration exciter, and an inertial element connected to a vibration exciter connected to a noisy room element

- to simplify the device and its installation on the object of noise, to increase its reliability and efficiency, to provide the ability to quickly install the device on various elements of the room and replace the vibration exciter and inertial element,

Significant changes and additions have been made, namely:

- the vibration exciter is installed directly on the noisy element of the room,

- the inertial element is pressed directly to the vibration exciter,

- the inertial element with the vibration exciter is pressed by an elastic clip to the noisy element,

- while the second end of the elastic clamp is fixed to a fixed or noisy element of the room.

In addition, the inertial element may have restrictive protrusions for holding the vibration exciter.

In addition, the noise generator can be placed on the inertial element.

In addition, the device can be equipped with a set of interchangeable clips and their mounts to various noisy elements of the room.

In addition, the device may have a set of interchangeable vibration exciters and inertial elements, the characteristics of which are selected for typical conditions of use of the device.

Embodiments of the claimed devices are presented in figures 1, 2, 3 and 4, in which the following notation is adopted: 1 - noise signal generator, 2 - vibration exciter, 3 - inertial element, 4 - noisy room framing element, 5 - elastic clamp, 6 - fixed element of the room, 7 - restrictive protrusions of the inertial element 2 for holding the vibration exciter, 8 - window glass, 9 - window frame, 10 - screw, attaching the second end of the elastic clip to the window frame, 11 - window glazing bead.

In FIG. 1 is a generalized diagram of a device with an elastic clamp mounted on a fixed element of the room, in FIG. 2 is a generalized diagram of a device with an elastic clip fixed to a noisy element; FIG. 3 and 4 are examples of attaching a device to a window.

The device of FIG. 1 is a vibration exciter 2 pressed by an inertial element 3 with restrictive protrusions 7 to a noisy framing element of a room 4. An inertia element 3 with a vibration exciter 2 is pressed by one end of an elastic clip 5 to a noisy framing element of a room 4. The second end of an elastic clip 5 is fixed to a fixed element of the room 6. The vibration exciter 2 is connected to the noise-like signal generator 1. When the noise generator 1 is turned on, the corresponding variable is applied to the vibration exciter 2 noise voltage, as a result of which its thickness fluctuates. This causes oscillatory movements of the inertial element 3 on the one hand and the noisy element 4 on the other hand. Since the mass of the inertial element 3 is greater than the moving mass (impedance) of the noisy element of the room 4, the amplitude of movement of the noisy element is many times greater than the amplitude of the inertia element itself and must also be many times greater than the amplitude of the "dangerous signal", which excludes the possibility of unauthorized listening.

The device of FIG. 2 differs from the device of FIG. 1 in that the second end of the elastic clip 5 is fixed to the noisy room element 4 and the generator of the electric noise signal 1 is structurally combined with the inertial element 3. The operation is identical to the operation described for the device of FIG. one.

In figures 3 and 4 presents examples of the most common applications of devices - mounting them to the window. In FIG. 3, the second end of the elastic pressing spring 5 is fixed to the window frame 9 with screws 10, in FIG. 4 - the second end of the elastic pressing spring 5 is simply slipped under the window glazing 11. Its operation is identical to that described for the device of FIG. one.

Theoretically, in order to maximize the amplitude of oscillations of element 4, it is necessary to maximize the inertial element 3. However, with a large mass of the inertial element, it is difficult to hold it with an elastic pressure spring on a noisy element. The author allowed a compromise between these requirements for the mass of the inertial element by experimentally measuring the noise characteristics of the device with several different masses of inertial elements.

In the technique of vibrational noise, energy ratios are usually characterized by logarithmic levels of vibration acceleration [10]. For example, an increase in vibration acceleration by 20 dB, i.e. 10 times, equivalent to an increase in vibrational power by the same 20 dB, i.e. 100 times.

To select the optimal mass of the inertial element, experiments were carried out, the results of which are shown in FIG. 5, where along the ordinate axis are vibration acceleration levels in dB relative to 1 μm / s ² created by the VP-3 vibration exciter (manufactured by Informakustika OJSC) on a window with three glasses (two-chamber double-glazed window), 0.7 m × 0.7 in size m. The abscissa is the frequency of the octave bands in Hz. A gauss-like noise electric signal with a voltage of 15 V _eff from a pink noise generator was supplied to the vibration exciter. Mounting was carried out using a clip attached to the window frame. Interchangeable inertial elements of different weights — 60, 85, 125, and 185 g — were used. The level of vibration acceleration created by the VP-3 vibration exciter glued to the glass without an inertial element was also measured.

The experiment showed that the level of vibration generated at the middle and upper frequencies depends little on the mass of the inertial element. But it is extremely dependent on its mass at low frequencies. For example, in the octave band of 125 Hz, the increment of levels due to the introduction of an inertial element is more than 32 dB with an inertial element mass of 125 g and more than 22 dB with a mass of 85 g. The latter is quite sufficient to create reliable low-frequency noise at a very low noise generator power. A further increase in weight to 185 g does not lead to a significant positive effect, but significantly complicates the means of holding the inertial element 3 with vibration exciter 2 on a vertical surface 4.

Similar experiments were conducted for other types of noisy room elements. Recommended masses of the applicant are given in the table.

The direct contact of the vibration exciter to the surface of the noisy element means that there is no vibration-absorbing layer between them.

Naturally, before installing the device, it is necessary to prepare the surface of the noisy room element: remove the layer of paint, drywall and wallpaper, if this is not possible, install a vibration-conducting anchor into the element body through the coating, or press another rigid object and vibration exciter directly to it.

As for the elastic clamp 5 - it performs two functions:

- balances the weight of the inertial element (fixes the position of the inertial element with the vibration exciter on the noisy element, prevents their displacement under the influence of gravity);

- presses the vibration exciter (through the inertial element) to the noisy element. The force of its clamp with a sufficiently large mass of the inertial element does not affect the efficiency of noise.

In some cases, manufacturers' recommendations should be followed, which recommend creating preliminary static compression of the vibration exciter to increase the linearity of the conversion of electrical noise into mechanical vibration.

The described examples of the device, of course, do not exhaust the entire variety of options covered by the claims.

Since the claimed device is extremely simple - it consists only of absolutely necessary elements, its reliability is incomparably higher than its analogues.

As noted above, in the description of analogues, attaching the device to the noise element with glue and screw leads to the weakening of such a fastening (deterioration of the quality of work) and even its destruction over time, since the fastening elements are mounted on a vibrating element. In the proposed device, this is excluded - the spring is durable and reliably presses it to the noise element.

As is obvious from the above, the claimed device is very easy to install on almost any object of noise. It is fixed with one single elastic clamp, the second end of which is fixed to a fixed element of the room or to a noise element. Given the small weight and size of the device, sometimes it is not even necessary to make a special hole to secure the second end of the clip - just screwing it on or using a strong clamp.

A great advantage of the proposed design is the ability to quickly replace vibration exciters and inertial elements. To do this, simply pull the clip and replace it. This makes the device universal, suitable for equipment of any premises, by choosing for each noise element the most suitable vibration exciter, inertial element and clamp. In this regard, it is advisable to have a set of the most popular interchangeable vibration exciters and inertial elements.

The claimed device is manufactured and tested by the applicant. The test results confirmed the expected advantages of the device and its advantages over analogues and prototype - it is incomparably simpler, easy to install on a noisy element, has a high efficiency, convenient for quick replacement of elements.

Its optimal design and, especially, the experimentally justified use of the corresponding inertial element, made it possible to significantly reduce the required power of the noise signal generator and constructively combine the noise signal generator with the inertial element.

Thus, the task of the invention is completed. A very simple design of vibration-induced noise suppression of channels of unauthorized leakage of an acoustic signal from a room has been created. The device has high radiation efficiency, high stability and reliability. It is universal in operation, because it is easily attached to any objects and allows you to quickly replace vibration exciters and inertial elements.

The main differences between the device and the prototype are:

- the vibration exciter is pressed directly to the noisy element,

- the inertial element is pressed directly to the vibration exciter,

- the inertial element with the vibration exciter is pressed against the noisy room element by an elastic clip, the second end of which is fixed to a fixed or noisy room element.

Variants of the device may contain other distinctive features, in particular, the inertial element may have restrictive protrusions for holding the vibration exciter, and the noise generator can be structurally combined with the inertial element.

These differences are useful, new, non-obvious for a specialist and industrially applicable, i.e. they meet all the criteria for inventions.

Information sources

1. US patent for the invention 4098370 H05K 5/00, publ. 1978.

2. US patent for the invention 4 010 324, H04J 3/00, publ. 03/01/1977.

3. RF patent for utility model No. 21490 (IPC7 H04K 3/00, publ. 02.20.2002).

4. RF patent for utility model No. 27442 (IPC7 H04K 3/00, published on January 27, 2003).

5. RF patent for utility model No. 49363 (IPC7 H01L 41 | 08, publ. 10.11.2005).

6. RF patent for the invention No. 2408143 (IPC7 H04K 3/00, publ. 12/27/2010).

7. Yu.G. Zadorozhniy, Darchuk A.D., Ogorodnichy N.V. Optimization of the characteristics of the vibrator of the piezoelectric low-frequency type VPN-1. http://piezosensor.com.ua/files/v1.pdf.

8. Glue curing. Products of LLC "Anna". http://npoanna.ru/Content.aspx?name=models.kley.01.

9. Buzov G.A., Kalinin S.V., Kondratiev A.V. Protection against information leakage through technical channels M .: Hot line - Telecom, 2005.

10. GOST 12.1.012-90 "Vibration safety. General requirements."

Claims (4)

1. The device vibrational noise channel leakage of acoustic speech information containing an electric noise signal generator connected to a vibration exciter, and an inertial element connected to a vibration exciter connected to a noisy room element,
characterized in that
the vibration exciter is pressed directly to the noisy room element, the inertia element is pressed directly to the vibration exciter and has restrictive protrusions to hold the exciter, the inertia element with the vibration exciter is pressed with an elastic clip to the noisy element, while the second end of the elastic clip is fixed to a fixed or noisy room. 2. The device according to p. 1, characterized in that the noise signal generator is structurally combined with an inertial element. 3. The device according to claim 1 or 2, characterized in that it is equipped with a set of interchangeable clips and their fastenings to the elements of the room. 4. The device according to p. 1 or 2, characterized in that it has a set of interchangeable vibration exciters and inertial elements, the characteristics of which correspond to the typical conditions of use of the devices.

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