EP0414865A1

EP0414865A1 - Process for masking the noise signals emitted by the sound-emitting mechanical elements of a vehicle, in particular a submerged submarine, and submarine.

Info

Publication number: EP0414865A1
Application number: EP90904230A
Authority: EP
Inventors: Guenther Laukien
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-03-16
Filing date: 1990-03-16
Publication date: 1991-03-06
Anticipated expiration: 2010-03-16
Also published as: DE3908578C2; US5208784A; JPH04501174A; DE3908578A1; WO1990010928A1; JP2681541B2; EP0414865B1

Abstract

Un procédé permet d'agir sur une source de bruits, notamment dans un sous-marin immergé (20). Le sous-marin agit comme source de bruits et émet un signal acoustique (S; 24, 25, 26) caractérisé par un premier spectre de fréquences avec au moins une première intensité maximale. Afin de rendre plus difficile la détection du spectre de fréquences par des systèmes (13) de localisation passive de bruits, le premier spectre de fréquences est stochastiquement modulé et/ou la fréquence de l'intensité maximale est décalée par altération de la source de bruits.A method makes it possible to act on a source of noise, in particular in a submerged submarine (20). The submarine acts as a source of noise and emits an acoustic signal (S; 24, 25, 26) characterized by a first frequency spectrum with at least a first maximum intensity. In order to make it more difficult to detect the frequency spectrum by passive noise location systems (13), the first frequency spectrum is stochastically modulated and / or the frequency of the maximum intensity is shifted by alteration of the noise source. .

Description

Method for influencing a sound source of a submarine and submarine

The invention relates to a method for influencing a sound source, in particular a submersible, wherein the sound source emits a sound signal with a first frequency spectrum with at least a first intensity maximum. The invention further relates to a submarine with sound-emitting mechanical elements and means for camouflaging the emitted sound signals.

The invention is intended, in particular, to mask the sound source or camouflage the submarine.

As part of the fight against submarines, both active and passive systems are used to locate the submarines,

With the active systems {e.g. SONAR) a search signal is emitted from a searching vehicle, for example a frigate, generally a sound signal in the sound or infrasound range. These sound signals are reflected on the surface of the submarine and reach receivers on board the searching vehicle, so that the position of the submarine can be determined from these received signals by means of suitable evaluation methods.

In order to protect submarines against such active locating methods, it is known to provide the submarine with a coating on its outer shell which absorbs incident sound signals as best as possible.

From DE-OS 33 32 754 an underwater ship is known which is to be camouflaged against detection by a low-frequency active sonar, ie a passive sound location system. For this purpose, broadband wedge absorbers are arranged in particular on the bow and on the bow side of the tower, which in turn are adapted to the respective ship contours and do not themselves have any sound reflection properties. In this way, the recognizability of the submarine, namely the so-called target dimension, should be reduced by approx. 10 to 15 dB. It has also already been proposed to reduce turbulence on the submarine parts around which water flows by introducing chemical additives (DE-OS 23 18 304).

Passive location methods, on the other hand, take advantage of physical phenomena that are caused by the submarine itself. For example, it is known to take advantage of the fact that the metallic parts of the submarine disrupt the earth's magnetic field when locating submarines. Positioning probes are therefore known which are based on the principle of nuclear magnetic resonance and are towed by ships or aircraft on a long line over the areas of the sea to be searched in order to detect faults in the earth's magnetic field. - -

Another passive location method, as described for example in EP-PS 63 517, EP-OS 120 520 and EP-PS 213 418, is based on the measurement of sound signals which are emitted by the submarine. A submarine in fact radiates sound to the surrounding sea water in the same way as moving parts in the submarine transmit vibrations to the outer skin. Measurable sound signals are primarily generated by moving propulsion elements of the submarine, i.e. by the rotating parts of the propulsion engine and by the shaft, but the rotating screw and the cavitation caused by the screw must also be taken into account as sound sources. Finally, sound signals are generated when the elevator and depth rudder are actuated, when deflating air and when shifting trimming masses, which can be detected on board modern frigates using correspondingly sensitive passive location systems. In this context, the special feature of submarines with a nuclear drive is that nuclear reactors, such as those used on board submarines, are usually equipped with periodically actuated control rods. The control rods are moved in the reactor vessel at a predetermined frequency, the immersion depth of the control rods being adjustable so that the power emitted by the nuclear reactor can be adjusted in this way. As a result of the periodic movement of relatively large masses, however, a relatively intense sound signal also arises which can be used to locate such submarines driven by nuclear technology.

On the other hand, it is known that with modern, increasingly sensitive passive sound locating systems, the sound that is present in the vicinity of the submarine must also be taken into account to an ever greater extent. This natural sound is essentially generated by ocean currents, waves, schools of fish and the like.

When operating passive sound location systems, this ambient sound becomes noticeable as noise, which can assume an even or an uneven frequency distribution depending on the ambient conditions.

A method is known from DE-OS 34 06 343 with which sound signals from submarines, the intensity of which is only slightly above that of the ambient noise, can be recognized from the ambient noise. Numerous measures are known for preventing submarines from being recognized by the passive sound location systems described above.

The essential measure is, of course, to reduce the overall sound emission of the submarine if possible. In order to achieve this, particularly low-noise machine parts, for example bearings, are used in the drive area of the submarine, so that the total sound energy generated is kept as low as possible.

In addition, however, it is also known to take sound insulation measures on board submarines in order to at least prevent unavoidable sound from reaching the outer shell of the submarine. For this purpose, it is known, for example, to design the outer shell of the submarine in two shells and to flood the space with a thickness of, for example, 30 cm with seawater, so that as little sound waves as possible can reach the outer shell of the submarine.

Furthermore, the extent of the emitted sound waves can also be reduced in hazardous situations by reducing the drive power by so-called "creep speed". However, this naturally degrades the submarine's ability to evade detection by enemy ships by removing them.

An electrical system for submarines is known from DE-OS 36 00 258, which has means for camouflaging the submarine. In the known system takes into account the fact that an AC network of the submarine in the fre frequency range between 60 Hz and 400 Hz works and that it is inevitable that frequencies in this frequency range plus their harmonics are emitted via the hull to the surrounding water. In the known electrical system, a frequency of, for example, 30 kHz is therefore provided for the alternating current network of the submarine, which frequency is far above the reception frequency range of other location systems.

However, this known electrical system has the disadvantage that it can only camouflage the submarine submerged as long as the frequency ranges of enemy passive location systems do not also operate in the range of 30 kHz, for example. As soon as the measures taken in the known system are known to the respective enemy, the enemy can locate the submarines submerged by checking the new frequency range by appropriately redesigning his passive location system.

Finally, it is also known to disrupt passive sound location systems on board enemy ships by placing objects that emit a high sound power and thus override the sensitive receivers of the passive sound location systems.

For example, from DE-OS 33 00 067 a device for disrupting the location of submarines is known, in which a body can be ejected from a submarine that is equipped with a sound-emitting device. This body is used to mislead a sonar system, ie an active acoustic location system on board an enemy vehicle. From EP-OS 237 891 a device for disturbing and deceiving waterborne sound locating systems is known. A supporting body of the known device is provided with pyrotechnic charges, the combustion of which leads to the impulsive release of gas bubbles, which, for example, cause low-frequency structure-borne noise vibrations and high-frequency oscillating outer cavitation layers on a housing, from which they also emerge to form a bubble curtain. The known device is intended to distract from an object to be protected and to simulate a reflecting target object due to the slowly floating bubbles.

However, the area of use of such interfering objects is limited to the case where the presence of the submarine on board the enemy ships is already known and the only thing that is to be prevented is that the passive sound location systems enable the precise location of shot torpedoes, which are also under Sound generation is in motion. Such interfering objects are unsuitable for the case in which a submarine wants to remain undetected at all.

The invention is therefore based on the object of developing a method and a submarine of the type mentioned at the outset in such a way that the location is made considerably more difficult, if not impossible, by passive sound location systems, in that the amplitude of the signals received by the passive sound location systems get into the area of natural noise and go under. According to the method mentioned in the introduction, this object is achieved according to the invention in that the first frequency spectrum is modulated by influencing the sound source.

According to the submarine mentioned at the outset, the object on which the invention is based is achieved in that means are provided for influencing the mechanical elements in such a way that a first frequency spectrum emitted by the mechanical elements is modulated.

The object underlying the invention is completely achieved in this way.

Modern passive sound locating systems, as already explained above, must first recognize sound signals from searched submarines as such before locating, i.e. a determination of the exact position of the submarine becomes possible. For this purpose, the passive sound locating system must distinguish the sound waves emitted by the submarine from the sound events in the natural environment, which is possible only because the sound signals emitted by the submarine stand out from the ambient sound. When the frequency spectrum is modulated, on the other hand, the radiated sound energy is additionally distributed on sidebands, so that the amplitude of the carrier signal is reduced accordingly and is ultimately lost in the noise of the ambient sound.

In a preferred embodiment of the invention, the frequency spectrum is modulated stochastically. This measure has the advantage that all regularities to which the sound signal obeys are switched off, so that the sound signal can no longer be recognized from the stochastic ambient sound.

These laws are based on the fact that the sound-generating elements are, as a rule, periodically or quasi-periodically actuated components of the submarine, for example a drive shaft or drive screw rotating at a predetermined speed. In such a case, the passive sound location system therefore only needs to search for those sound signals in the ambient noise that have a pronounced intensity distribution of the frequency spectrum, because such sound events do not occur in the natural ambient noise.

If, according to the invention, the sound emitted by the submarine is now influenced in such a way that the sound-triggering mechanical processes are robbed of their regularity, the passive sound locating system cannot consequently distinguish these sound signals, which no longer obey regularities, from the likewise stochastic sound signals of the environment.

Ideally, this means that no characteristic signals appear in the frequency spectrum of the ambient sound measured by the passive sound system, but at least these signals are so reduced in intensity, namely in the frequency range, that they are no longer affected by the natural irregularities of the spectral distribution of the ambient sound can be distinguished. In a preferred embodiment of the method according to the invention, the movement sequence is modulated by mechanical elements forming the sound source.

This measure has the advantage that any spectral distribution of the emitted sound signals can be achieved by mechanically influencing the main causative elements in order to achieve the objectives described above.

In one embodiment, this variant can be modulated in the case of macroscopically moving mechanical elements.

"Macroscopically moved" is to be understood here to mean those parts which are visibly moved, for example, in the drive train of the submarine, for example rotating shafts, engine parts, drive screws and the like. If these macroscopically moved elements are frequency-modulated, this means in the spectral range Distribution of the emitted sound signals so that a large number of sidebands are formed, the frequency spacing and amplitude of which, due to the stochastic modulation, vary constantly according to random factors, so that no regular appearance remains in the emitted sound image. Furthermore, it is particularly advantageous that, in the case of intensive frequency modulation, the radiated power is distributed to the carrier and the sidebands, so that a previously monochromatic signal with a small bandwidth and a large amplitude is now converted into a smoothed signal with a large bandwidth and low amplitude is implemented. As a result of the large number of sidebands in frequency modulation, a spectral distribution with an irregular envelope curve arises, the shape of which fluctuates constantly as a result of the stochastic modulation. Alternatively, the movement amplitude can also be modulated for macroscopically moved mechanical elements.

In the case of amplitude modulation, as is well known, only two sidebands occur at a spacing from the modulation frequency, however, due to the stochastic amplitude modulation, the amplitude and position of the sidebands also vary constantly in this procedure, so that - although to a lesser extent - the advantages of the Fre¬ described above set frequency modulation.

The method described above can be used advantageously to disguise sound sources_de ^ yjersch, iedensten.Art, as well as to disguise sound sources in the form of land or aircraft of all kinds, however, as already explained, the method for camouflaging is particularly preferred of a submersible submerged, in which case the movement sequence of drive elements of the submarine is then preferably modulated.

This measure has the advantage that the essential sound-generating elements, namely the drive elements, are influenced in such a way that the sound signals emitted by them are obscured in the manner described.

It is particularly preferred if the speed of a drive shaft of the submarine is modulated.

This has the advantage that the main sound-generating element, namely, the drive chain of the submarine is influenced in the manner mentioned, so that a considerable Re _d u¬ total radiated sound power cation is possible. In a variant of the method according to the invention, the natural frequency is modulated by self-resonant mechanical elements forming the sound source.

This measure is advantageous if the radiated sound power is not only generated, or at least not essentially, by the macroscopically moving mechanical elements in the definition explained above, but rather an increase in the resonance of primary vibration events occurs due to self-resonant mechanical elements. In this case, the sound radiation can be influenced in an advantageous manner by modulating the natural frequency of these resonant elements.

In the preferred application case already described for submersible submersibles, the natural frequency of resonant components of the submarine is then modulated.

This is particularly advantageous because the mechanism described, e.g. for submarines, e.g. can occur in that primary vibration events, for example teams moving around in the submarine, are converted into sound events by the resonance exaggeration of components capable of resonance, the amplitude of which can take on considerable dimensions.

Another particularly preferred variant of the method according to the invention is that the sound source is in an environment with extraneous sound, that a second frequency spectrum of the extraneous sound is recorded, that second intensity maxima of the second frequency spectrum are determined and that by influencing the sound source the first frequency spectrum is shifted with its first intensity maximum to the frequency of one of the second intensity maxima of the second frequency spectrum. These measures, which can also be used on their own, have the significant additional advantage that the sound source, with its radiated sound power which can no longer be reduced, can "hide" in an intensity maximum of the ambient sound. In the analysis of the ambient sound detected by the passive sound location system, such changes in the spectrum that occur in isolation are naturally more noticeable, whereas only a variation of a naturally present maximum is much more difficult to identify.

This variant of the method according to the invention can also be used with particular advantage for camouflaging a submersible submersible, namely by recording the second frequency spectrum of the sea surrounding the submarine and the frequency of the movement sequence of drive elements of the submarine to the frequency of one of the second intensity maxima is moved.

When using this method, it can be added to the above-mentioned points of view that it is even conceivable to hide the submarine with the maximum of its emitted sound spectrum in the maximum of the ambient sound that is generated by the hostile vehicle searching for it. Since the enemy vehicle, for example the frigate, has to move during the search run, it naturally also emits a sound spectrum which has pronounced maxi a. If the sound-generating elements of the submarine are influenced in such a way that the maximum of the radiated sound spectrum corresponds to the maximum of the sound spectrum emitted by the frigate, it is particularly difficult for the passive sound locating system on board the frigate to detect this sound event because naturally the frigate drive in the immediate vicinity is a particular disturbance for the passive sound location system.

Of course, even with this variant of the method according to the invention, the natural frequency of naturally resonant components of the submarine can be changed in such a way that the radiated frequency spectrum is shifted to the maximum of the ambient sound.

According to the submarine according to the invention, a large number of variants of the apparatus configuration are possible in order to achieve additional advantageous effects in solving the task specified above.

Thus, in a preferred embodiment of the submarine according to the invention, an actuating stage can be provided in a supply unit of a drive motor.

This measure has the advantage that e.g. the speed of the drive motor, when using an electric motor, can be influenced by varying the supply voltage or supply frequency in order to produce the effects described in detail.

In a further variant, an adjustable clutch can be arranged in a drive train of the submarine. This measure has the advantage that the desired influencing of the sound-generating elements can also be achieved by stochastic opening and closing of the coupling, a coupling being a particularly suitable machine element, since it is intended for the separation and closing of a power flow in a drive train is provided. In a further preferred variant, auxiliary energy can be fed into a drive train of the submarine depending on the control stage.

This measure has the advantage that the sound-generating events are also influenced in the desired manner by stochastic feeding in of the auxiliary energy.

In a practical embodiment of this variant, an auxiliary energy store can be connected to the drive train via an adjustable coupling.

This measure has the advantage that the drive power or a part thereof can alternatively be used for charging the auxiliary energy store by selective closing and opening of clutches and the auxiliary energy store can then be partially or completely discharged again by coupling to the output of the drive train .

In a further variant of the invention, a transmission which can be set in the transmission ratio is arranged in a drive train of the submarine.

This machine element, which is known per se, also enables stochastic adjustment of the drive speed in a relatively simple manner.

In another variant of the invention, a resilient transmission element is arranged in a drive train of the submarine and can be bridged by means of an adjustable coupling. This measure also has the advantage that the sound waves generated are influenced in the desired manner by stochastically changing the elasticity of the drive train.

The same applies if, in a further embodiment of the invention, a transmission element is arranged in a drive train of the submarine, in which the phase position of a drive movement at the output can be set relative to the drive movement at the input.

In this way, phase modulation of the drive speed can be achieved, which likewise leads to the desired side bands and the distribution of the sound energy.

Furthermore, an embodiment of the invention is preferred in which means are provided for setting an angle of attack of a drive screw of the submarine.

This measure has the advantage that existing components can largely be used anyway, because it is known to vary the drive power of the submarine by adjusting the angle of attack of the drive screw.

In the case of a submarine with a nuclear drive with periodic deflection of control rods of a nuclear reactor, it is particularly preferred if a movement unit for the control rods can be set.

This measure has the advantage that the sound-causing movement of the control rods can also be obscured in the manner described. Another preferred variant of the invention is characterized in that adjustable mechanical clamping means are arranged on self-resonant elements.

This measure has the advantage that the natural resonance of the elements mentioned can be varied in a simple manner by exerting a mechanical tensile or compressive stress on the elements mentioned in a stochastic manner.

This is possible in a particularly simple manner if the clamping means are piezo elements, because piezo elements are particularly simple voltage / pressure converters, and the natural resonance of the elements mentioned can thus be easily modulated by electrical signals.

The same applies if the natural resonance of the elements is changed by the fact that adjustable mechanical coupling means are arranged between self-resonant elements.

Further advantages result from the description and the attached drawing.

It goes without saying that the features mentioned above and those still explained below can be used not only in the respectively specified combination but also in other combinations or on their own without departing from the scope of the present invention.

This applies in particular to the two process variants of frequency modulation and frequency shift, which can be used either in combination or individually, depending on the application. Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following drawing. Show it:

1 shows a schematic view of a combat situation in which a frigate tries to locate a submersible submarine by means of a passive sound locating system;

2 shows a schematic representation of the spectral distribution of sound signals over frequency for the sound events of a natural marine environment;

3 shows a periodic sound signal in the time domain;

4 shows the spectral distribution of FIG. 2, but with the simultaneous occurrence of the monochromatic sound event according to FIG. 3;

FIG. 5 shows the sound event from FIG. 3, but for the case of periodic amplitude modulation;

FIG. 6 shows the spectral distribution of FIG. 4, but for the sound event of FIG. 5;

Fig. 7 shows the sound event of Fig. 3, but for the _d

Case of stochastic amplitude modulation;

FIG. 8 shows the spectral distribution of FIG. 2, but in the presence of the sound signal according to FIG. 7; FIG. 9 shows the sound event of FIG. 7, but with a shifted carrier frequency;

FIG. 10 shows the spectral distribution of FIG. 8, but for the sound event of FIG. 9;

11 is an extremely schematic block diagram of a

Drive train of a submarine with a stochastically influenced control stage in the power supply of an electric motor;

FIG. 12 shows a block diagram similar to FIG. 11, but with a stochastically influenced separating clutch in the drive train;

FIG. 13 shows a block diagram similar to FIG. 11, but with the stochastically influenced connection of an auxiliary energy store;

FIG. 14 shows a block diagram similar to FIG. 11, but with a stochastically influenced transmission gear;

15 shows a block diagram similar to FIG. 11, but with a stochastically influenced elastic transmission element;

16 shows a block diagram similar to FIG. 11, but with a stochastically influenced phase shifter in the drive train;

FIG. 17 shows a block diagram similar to FIG. 11, but with stochastically influenced adjustment of the inclination angle of the drive screw; 18 shows a schematic representation of a nuclear reactor for driving a submarine with stochastically influenced adjustment of the control rods;

19 shows a schematic illustration for explaining a stochastic setting of a natural frequency of an inherently resonant spring-mass system;

20 shows a variant of the arrangement according to FIG. 19 with stochastically set coupling between two self-resonant spring-mass systems.

In the combat situation shown in FIG. 1, 10 denotes a sea on which a frigate 11 is located in search of submarines.

Below a water line 12 of the frigate 11, the frigate 11 is provided with a passive sound location system 13, which has an opening cone 14, for example. The frigate 11 in turn generates sound waves 15, in particular by driving the frigate 11.

Below the surface of the sea 10 is a submarine 20 with a nuclear drive 21, not drawn to scale, with 22 is a drive shaft of the submarine 20, which leads to a screw 23. With 24, 25 and 26 sound waves are referred to, which are emitted from the submarine 20.

24 is intended to symbolize the proportion of sound waves that is generated by the movement device of the control rods of the nuclear drive 21, as will be explained further below in relation to FIG. 18. 25 is intended to symbolize the proportion of sound waves that are generated by the drive elements of submarine 20, in particular by the rotating shaft, the rotating motor elements and the like.

Finally, 26 is intended to symbolize the portion of the sound waves that is generated by the rotation of the screw 23, in particular by the cavitations caused by the screw 23.

For its part, the submarine 20 is also equipped with a passive sound location system 27 which sweeps over a cone 28.

A passive sound location system is to be understood below to mean any device that is able to receive and analyze sound signals.

2, the intensity of a sound signal S is plotted as the first frequency spectrum 30 over the frequency f. The first frequency spectrum 30 is intended to represent the natural environment in the absence of artificial sound sources. As can be seen from fi, the first frequency spectrum 30 is provided with a first maximum 31, which is generated by natural environmental influences, for example by a swell associated with a specific wind strength.

It is understood that in the context of the present invention the frequencies of interest are in the sound or infrasound range.

3 shows in the time domain t a first sound signal 32 of a sinusoidal, ie periodic shape, which is intended to symbolize a sound signal US emitted by a submarine. The frequency of the first sound signal 32 can for example correspond to the speed of the shaft 22. For the sake of clarity, harmonics and other phenomena are not taken into account in the representation of FIG. 3 and the following figures.

If the submarine 20 comes into the area of the cone 14 of the passive sound location system 13 of the frigate 11, then a superimposed, pronounced second frequency spectrum 33 appears in the first frequency spectrum 30, which in the idealized case of the monochromatic sound event of the first sound signal 32 of FIG. 3 corresponds to a high narrow line at a frequency ± 2 of the wave.

As can be clearly seen from FIG. 4, the second frequency spectrum 33 in the form of the narrow line can be clearly distinguished from the background of the first frequency spectrum 30.

FIG. 5 now shows the case in which the first sound signal 32a is periodically amplitude-modulated, as illustrated with a periodic envelope 34 in FIG. 5. As is known, sidebands arise from an amplitude modulation at a distance of the modulation frequency from the carrier, which is evident in FIG. 6 in the first frequency spectrum 30 by a superimposed second frequency spectrum 33a, which now has sidebands 35. The amplitude of the carrier is significantly reduced compared to the unmodulated case in FIG. 4 because the sound power is now distributed over the carrier and the two side bands. However, the second frequency spectrum 33 can still be clearly distinguished from the background of the first frequency spectrum 30. FIG. 7 now shows a further step in which the first sound signal 32b is stochastically amplitude modulated, which is indicated by a stochastic envelope 36.

"Stochastic" should be understood to mean any procedure that is generated by a random generator or in any other way and that is not subject to any laws.

The stochastic amplitude modulation of the first sound signal 32b manifests itself in the spectral representation of FIG. 8 in a second frequency spectrum 33b, which is now greatly broadened and the amplitude is correspondingly reduced because the radiated sound power is now distributed over a wide frequency range.

As can be clearly seen from FIG. 8, the distinction of the second frequency spectrum 33b from the surroundings of the first frequency spectrum 30 is already quite difficult and is only possible if the undisturbed first frequency spectrum 30 according to FIG. 2 was considered and now with the frequency f_. suddenly there is an increase in the plateau.

Fig. 9 now shows that with unchanged amplituden¬ stochastically modulated first sound signal 32c now whose frequency has been increased and ^'in such a way that the carrier frequency with the frequency fi of the first maximum corresponds 31st

This is expressed in the frequency range of FIG. 10 by the fact that the first maximum 31 was only slightly increased by the second frequency spectrum 33c. However, there is no fundamental change in the shape of the first frequency spectrum 30 because, as in the previous case in FIG. 8, it is not at a position at which there was no maximum before. a maximum occurs, but because only an existing maximum is only slightly increased in its amplitude.

It is obvious that this slight change in the first frequency spectrum 30 is particularly difficult, if at all, to be recognized.

FIG. 11 shows a drive train of submarine 20 in an extremely schematic block diagram.

A drive screw 40 is driven by an electric motor 41, which in turn is fed from batteries 44 via a thyristor stage 42. The thyristor stage 42 is controlled by an actuating stage 43, which makes it possible either to vary the speed of the electric motor 41 stochastically or to shift it from a first value to a second value, as is the case with the shift from ± 2 to fi in FIG. 10 has been explained.

If one considers the electric motor 41 in FIG. 11 as a structure with monochromatic sound generation, it can easily be seen that a frequency shift or frequency modulation of the speed n can be achieved by means of the setting stage 43, so that the situation arises as it is shown in FIG 2 to 10 for the case of amplitude modulation.

FIGS. 12 to 17 show variants of the block diagram according to FIG. 11, with elements that match are identified by the same reference numerals, but with the addition of a small letter.

12 shows a first variant in which a first clutch 45 is arranged between the electric motor 41a and the drive screw 40a. The control stage 43a controls the first clutch 45 in this case.

By opening and closing the first clutch 45, the speed of the drive screw 40a can be pulse-modulated, so that the desired sidebands are also set, and in the case of stochastic pulse modulation the desired stochastic distribution of the sidebands is set.

In the further variant shown in FIG. 13, in addition to the first clutch 45b, a second clutch 46 is arranged, by means of which a flywheel 47 or another kinetic energy store can be shifted into the drive train via a summation gear, which is only indicated at 48.

The clutches 45b, 46 are actuated by the actuating stage 43b, so that by selectively opening and closing these clutches 45b, 46 either the electric motor 41b works on the drive screw 40b as well as on the flywheel 47 when the clutches 45b and 46 are closed or when the first clutch 45b is open and the second clutch 46 is closed, only the flywheel 47 is working on the drive screw 40b or when the first clutch 45b is closed and the second clutch 46 is open, only the electric motor 41b is driving the drive screw 40b.

Modulation of the drive speed and thus of the sound-generating drive elements is also possible in this way.

In the next variant of FIG. 14, a continuously variable transmission 49 is connected between the electric motor 41c and the drive screw 40c. The control stage 43c controls the stepless Gear 49 on, so that the transmission ratio is varied stochastically, which likewise leads to a stochastic variation in the speed of the drive screw 40c.

In the further variant in FIG. 15, an elastic transmission element 51 is arranged between the electric motor 41d and the drive screw 40d and can be bridged by means of a third coupling 50. The third clutch 50 is controlled by the actuating stage 43d.

When the third clutch 50 is open, the drive train is relatively soft due to the now switched-on elastic transmission element 51, while when the third clutch 50 is closed, the drive train is correspondingly stiff. The desired effect can also be achieved by stochastic switching back and forth between these two states.

In the further variant of FIG. 16, a differential 42 is connected between the electric motor 41e and drive screw 40e, in which the two bevel gears located directly in the drive train rotate at the same speed, but in opposite directions, while the third, with its axis at right angles to it ordered bevel gear in a plane perpendicular to the plane of FIG. 16 is pivotable about the axis of the drive train. This pivoting movement produces a phase shift between the rotary movement at the input and at the output of the differential 52. The control stage 43e now stochastically adjusts the third bevel gear in this plane, so that the drive of the drive screw 40e is phase-modulated.

In the variant in FIG. 17, an actuation unit 53 is finally provided for the setting angle 54 of the drive screw 40f and the actuation unit 53 is controlled by the actuating stage 43f. In this case, the angle of attack 54 is modulated stochastically, which also leads to the formation of side bands.

18 schematically shows a nuclear reactor 60 which is part of the nuclear drive 21 of the submarine 20.

The nuclear reactor 60 has a reactor vessel 61 in which, in a known manner, control rods 62 can be moved axially by means of an actuating unit 63 in order to be able to adjust the power emitted by the nuclear reactor 60.

The actuating unit 63 is acted upon stochastically by the actuating stage 43e, so that the control rods 62 are displaced axially in a random manner in the reactor vessel 61. It is understood that the arrangement can be made such that the time integral of the immersed state of the control rods 62 is nevertheless e.g. can be kept constant in order to keep the output of the nuclear reactor 60 constant.

While the exemplary embodiments described above with reference to FIGS. 11 to 18 all affected the movement sequence of macroscopically moving elements on board a submarine, FIGS. 19 and 20 illustrate extremely schematically situations in which it is not the movement sequence but rather the natural frequency is influenced by resonant elements.

19, 70, 71 denote two fixed points, for example opposite walls of the outer shell of submarine 20 or a cabin on board submarine 20. A mass 72 is connected via springs 73 and 74 to fixed points 70, 71. The mass 72 can thereby, for example, a battle _d Stan or symbolize a walk in submarine 20 that is undertaken by teams of submarine 20. The aisle or command post, symbolized by the mass 72, is, however, capable of resonance due to the resilient suspension, so that an oscillation at the fixed points 70, 71 can be given off by the walking movement of teams as a result of the resonance exaggeration of the system.

In order to be able to influence the natural resonance of the system shown in FIG. 19, the coupling of the spring 74 to the second spatially fixed point 71 is interrupted by a piezo element 75 which is acted upon by the actuating stage 43h.

In this way, the rigidity of the system shown in FIG. 19 and thus its natural resonance can be influenced. This means that if the system excitation remains unchanged, e.g. by walking teams, the frequency of the emitted sound signal is shifted with the natural resonance.

20 shows a variant of this, in which a second mass 80 is additionally provided, so that two vibratory structures 72/73 and 74/80 are arranged between the fixed points 70, 71. The piezo element 75i in this case symbolizes the coupling between the two vibratory systems 72/73 and 74/80 and is acted upon by the actuating stage 43i.

By varying the coupling, the natural resonance of the overall system is also influenced in this case, so that the effect described above is achieved. The present application is linked to the following applications by the same applicant on the same day and the disclosure content of those applications is also made the disclosure content of the present application by this reference:

Patent application P 39 08 577.5

"Method and device for reducing the sound emission of submarines submerged"

Patent application P 39 08 576.7

"Method and apparatus for locating contained in aqueous environment proton poor objects, in particular for locating ^submarines' or sea mines in an ocean or an inland water"

Patent application P 39 08 575.9

"Underwater vehicle with a passive optical observation system"

Patent application P 39 08 574.0

"Procedures for operating submersible submersibles and

Submarine "

Patent application P 39 08 572.4

"Method and device for reducing the sound emission of submarines submerged"

Patent application P 39 08 573.2

"Method and device for operating submerged

Submarines "

Claims

1. A method for influencing a sound source, in particular a submersible submerged (20), the sound source emitting a sound signal (S; 24, 25, 26) with a first frequency spectrum (33) with at least a first intensity maximum, characterized thereby that the first frequency spectrum (33) is modulated by influencing the sound source.

2. The method according to claim 1, characterized in that the frequency spectrum (33) is modulated stochastically.

3. The method according to claim 1 or 2, characterized in that the movement sequence is modulated by mechanical elements forming the sound source.

4. The method according to claim 3, characterized in that the movement frequency (f) is modulated in macroscopically moving mechanical elements.

5. The method according to claim 3, characterized in that the movement amplitude is modulated in macroscopically moving mechanical elements.

6. The method according to one or more of claims 3 to 5, characterized in that for camouflaging a submerged submarine (20) the movement sequence of propulsion elements of the submarine (20) is modulated.

7. The method according to claim 4 and 6, characterized in that the speed (s) of a drive shaft (22) of the submarine (20) is modulated.

8. The method according to one or more of claims 1 to 7, characterized in that the natural frequency is modulated by the resonant mechanical elements forming the sound source.

9. The method according to claim 8, characterized in that for camouflaging a submersible submarine (20), the natural frequency of resonant components of the submarine sub (20) is modulated.

10. The method in particular according to one or more of claims 1 to 9, characterized in that the sound source is in an environment with external noise, that a second frequency spectrum (30) of the external noise is recorded, that second intensity maxima (31) of the second Frequency spectrum (30) are determined and that by influencing the sound source, the first frequency spectrum (30) with its first intensity maximum is shifted to the frequency (fi) of one of the second intensity maxima (31) of the second frequency spectrum (30).

11. The method according to claim 10, characterized in that for camouflaging a submersible submarine (20), the second frequency spectrum (30) of the submarine

⁽ 20) surrounding sea (10) is recorded and that the frequency (f2 ^{) of} the movement sequence of propulsion elements of the submarine (20) is shifted to the frequency (fi) of one of the second intensity axima (31).

12. The method according to claim 10, characterized in that for camouflaging a submersible submarine (20), the second frequency spectrum (30) of the submarine (20) surrounding the sea (10) is recorded and that the natural frequency of resonant components of the submarine ( 20) is shifted to the frequency (fi) of one of the second intensity maxima (31).

13. Submarine with sound-emitting mechanical elements ⁽ 21, 22, 23) and means for camouflaging the emitted sound signals (S), characterized in that means for influencing the mechanical elements ⁽ 21, 22, 23) are provided, such that one of the first frequency spectrum (33) emitted by the mechanical elements (21, 22, 23) is modulated.

14. Submarine according to claim 13, characterized gekεnnzεichnet that the first frequency spectrum (33) is modulated stochastically.

15. Submarine, in particular according to claim 13 or 14, characterized in that the means for influencing the mechanical elements (21, 22, 23) move the first frequency spectrum ⁽ 33 ⁾ in its frequency position (f ₂ ).

16. Submarine according to claim 15, characterized in that the mechanical elements (21, 22, 23) are moving Antriebsεlεmente the submarine (20) and that means for adjusting the frequency of movement of the drive elements are provided in the drive.

17. Submarine according to claim 16, characterized in that an actuating stage (43) in a supply unit (42, 44) of a drive motor (41) is provided.

18. Untersεeboot according to claim 16, characterized in that an adjustable clutch (45, 45b) is arranged in a drive train of the submarine (20).

19. Submarine according to one or more of claims 16 to 17, characterized in that auxiliary energy can be fed into a drive train of the submarine (20) as a function of the actuating stage (43b).

20. Submarine according to claim 19, characterized in that a Hilfsenεrgie memory (47) via an adjustable coupling (46 ^{) can be connected} to the drive train.

21. Submarine according to one or more of claims 16 to 19, characterized in that in a power train of the submarine (20) a transmission ratio (ü) adjustable gear (49) is arranged.

22. Submarine according to ^' one or more of claims 16 to 20, characterized in that a resilient transmission element (51) is arranged in a drive train of the submarine (20), which can be bridged by means of an adjustable coupling (50) .

23. Submarine according to one or more of claims 16 to 22, characterized gekεnnzεichnεt that a transmission element (52) is arranged in a drive train of the submarine, in which the phase position of a drive movement at the output can be adjusted relative to the drive movement at the input.

24. Submarine according to one or more of claims 16 to 23, characterized in that means are provided for adjusting an angle of attack (54) of a drive screw (40f) of the submarine (20).

25. Submarine according to one or more of claims 16 to 24, characterized in that in the case of a nuclear drive (21) with periodic deflection of control rods (62) of a core actuator (60), a movement unit (63) for the control rods ( 62) is adjustable.

26. Submarine according to one or more of claims 13 to 25, characterized in that adjustable mechanical tensioning means are arranged on resonant elements (72, 73, 74).

27. Submarine according to claim 26, characterized in that the clamping means are piezo elements (75).

28. Submarine according to one or more of claims 13 to 27, characterized in that adjustable mechanical coupling means (43i, 75i) are arranged between intrinsically resonant elements (72, 73; 74, 80).