AU2020335136B2

AU2020335136B2 - Locating signal receiver for determining a sound pulse mapping

Info

Publication number: AU2020335136B2
Application number: AU2020335136A
Authority: AU
Inventors: Johannes Gelze; Rhys Roberts; Jan-Philip Schwarz
Original assignee: ThyssenKrupp AG; Atlas Elektronik GmbH
Current assignee: ThyssenKrupp AG; Atlas Elektronik GmbH
Priority date: 2019-08-23
Filing date: 2020-08-14
Publication date: 2023-12-14
Anticipated expiration: 2040-08-14
Also published as: WO2021037589A1; EP4017800A1; DE102019212636A1; AU2020335136A1

Abstract

The invention relates to a device (20) for receiving underwater sound with a plurality of underwater sound receiving assemblies (22), an underwater sound receiving assembly (22) comprising an underwater sound receiver (26), a sound reflector (28) and a sound window (24). A first underwater sound receiving assembly (22) is arranged adjacent to a second underwater sound receiving assembly (22) and a third underwater sound receiving assembly (22) is arranged adjacent to the second underwater sound receiving assembly (22). The first and the second underwater sound receiving assemblies (22) are at a first distance from one another and the second and the third underwater sound receiving assemblies (22) are at a second distance from one another, the first and the second distances being different from one another.

Description

Locating signal receiver for determining a sound pulse mapping

1. FIELD OF THE INVENTION The invention relates to a device for receiving underwater sound, in particular an array of underwater sound receiving assemblies, wherein an underwater sound receiving assembly respectively comprises an underwater sound receiver, also called a hydrophone or sound transducer, a sound window, through which sound waves can pass so that an underwater sound receiver arranged behind the sound window can detect the sound waves, and a sound reflector which can reflect sound waves (onto the hydrophone). The device can also be referred to as a sonar system.

2. BACKGROUND OF THE INVENTION Sonar systems, which are arranged in or on water vehicles, in particular ships or submarines, presently have an equidistant spacing between the individual hydrophones to simplify the evaluation of the individual hydrophone signals. In particular the beamforming is simplified if the hydrophones are arranged on a straight line. However, this has the disadvantage that the array can only be attached to surfaces of the water vehicle which have no or only minor curvature. At curved points, hydrophones are fastened by means of a spacer on the water vehicle so that the hydrophones are still arranged on a straight line. At points having a strong curvature, the hydrophones therefore accordingly protrude far from the water vehicle. Furthermore, an arrangement, for example, around the bow of the water vehicle is not possible. The sonar system is also attached to the outer hull of the water vehicle and can at least not completely be arranged in the interior of the water vehicle, so that the sound windows terminate with an outer hull of the water vehicle. However, in particular in the case of submarines this has the disadvantage that at points at which the sound window stands out from the outer hull, eddies occur. However, eddies generate sound waves which, especially in the case of submarines, which are to travel as quietly as possible so as not to be recognized, are undesired.

An object of the present invention is therefore to provide an improved concept for devices for receiving underwater sound, in particular sonar systems.

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3. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a device for receiving underwater sound, i.e. an array comprising a plurality of underwater sound receiving assemblies. One, in particular each, underwater sound receiving assembly has an underwater sound receiver, a sound reflector, and a sound window. Alternatively, a common sound window may be provided for the underwater sound receiving assemblies arranged in the array. A first one of the underwater sound receiving assemblies is arranged adjacent to a second one of the underwater sound receiving assemblies and a third one of the underwater sound receiving assemblies is arranged adjacent to the second underwater sound receiving assembly. The first and the second underwater sound receiving assemblies have a first spacing to one another and the second and the third underwater sound receiving assemblies have a second spacing to one another, wherein the first and the second spacings differ from one another. In other words, the underwater sound receiving assemblies, in particular the corresponding underwater sound receivers are not arranged equidistantly, they thus have the absence of an equidistant distance to one another. The underwater sound receiving assemblies can be connected by means of a bus system to provide audio signals to an evaluation unit. Relevantly, the underwater sound receiving assemblies form separate, individual modules.

The concept is based on forming small individual modules, which respectively comprise an underwater sound receiver, a sound window, and a sound reflector, and arranging them so that they are adapted to a shape of the water vehicle. In prior art devices, the modules have previously each comprised a large number of hydrophones, whereby an individualization of the shape of the device is not possible. By means of the small modules, the underwater sound receivers can be arranged, for example, inside the outer hull of the water vehicle, for example in the hull of the ship or inside the hull of the submarine. The sound windows then close the outer hull watertight and can thus in particular withstand the water pressure. The underwater sound receivers are arranged in a chamber behind the sound window. The chamber is filled with water. However, a water exchange of the water enclosing the water vehicle with the water in the chamber can take place through the outer hull or the sound windows. The sound propagation in the chamber is thus as similar as possible to the sound propagation on the other side of the sound window.

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In exemplary embodiments, the underwater sound receiving assemblies are arrayed along a curved line. This enables the adaptation of the shape of the sonar systems to an arbitrary shape. In particular, the line can have a curvature in a first direction and in a second direction. Due to the curvature in two directions, the array of underwater sound receiving assemblies can extend in a plane in different directions. Due to the curvature in the first direction and the second direction, the line, thus the array of the underwater sound receiving assemblies, can experience a profile in three spatial directions.

If the underwater sound receiving assemblies are arrayed along a curved line, a one dimensional or one-line array of the underwater sound receiving assemblies is provided. However, a multidimensional or multiline array of the underwater sound receiving assemblies can also be provided. The device then has a plurality of curved lines along which the underwater sound receiving assemblies are arrayed. In particular, the underwater sound receiving assemblies then form a surface or a surface array. Adjacent curved lines of the plurality of curved lines can have the absence of an equidistant spacing. This is advantageous so that the (surface) array of the underwater sound receiving assemblies can be adapted to the outer hull of the water vehicle.

In addition to the adaptation to the shape of the water vehicle, a frequency response of the device for receiving underwater sound can also be adapted by the use of the underwater sound receiving assemblies (as small modules). The frequency response may be adjusted, for example, in that the spacing between sound reflector and underwater sound receiver is varied in different underwater sound receiving assemblies. In other words, a spacing of the underwater sound receiver from the sound reflector of the plurality of underwater sound receiving assemblies differs from one another. The wavelength of the sound waves, which are constructively superimposed in the underwater sound receiver after prior reflection at the sound reflector and without reflection at the sound reflector, can be adjusted by the spacing of the sound reflector to the underwater sound receiver. The equivalent frequency of the sound waves which are constructively superimposed is also referred to as a design frequency.

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Furthermore, a size of the underwater sound receivers of the plurality of underwater sound receiving assemblies can also differ from one another. Thus, for example, the resonant frequency of the underwater sound receiver is adjusted. This is typically operated outside the resonant frequency, however it can be reasonable, in particular in the case of high design frequencies, to change the size of the underwater sound receiving assembly in such a way that the resonant frequency of the underwater sound assembly is also increased, so as not to be in the vicinity of the design frequency with the resonant frequency. At a higher resonant frequency, the sensitivity curve of the underwater sound receiver then still extends linearly even at greater sound frequencies.

In exemplary embodiments which relate to the underwater communication, however, it can also be reasonable to operate the underwater sound receiver in the vicinity of its resonant frequency. The (targeted) data exchange underwater by means of sonar is referred to as underwater communication. In the vicinity of the resonant frequency, the underwater sound receiver then has a greater reception sensitivity. Furthermore, the nonlinearity of the sensitivity curve is less relevant in the case of underwater communication since typically a narrow, predetermined frequency band is used for the data exchange. Signal processing is therefore still readily possible. The signal processing would be made significantly more difficult, however, in the case of a broadband signal as is typically provided in the case of locating by means of sonar, in the case of a nonlinear sensitivity curve as is present in the vicinity of the resonant frequency.

Furthermore, a water vehicle having a body which is delimited by an outer hull is disclosed, wherein the outer hull is designed to be in contact with water, in particular salt water or ocean water. The plurality of underwater sound receiving assemblies are installed in the water vehicle in such a way that the sound windows enable a sound wave to be incident in the body, wherein the associated underwater sound receivers are arranged in the body between the sound windows and the associated sound reflectors. The sound windows can close an opening of the outer hull. The closing can take place in such a way that the sound windows terminate with the outer hull, that is to say that the sound windows are formed in such a way that they

4 20216573_1 (GHMaters) P117465.AU emulate the missing parts of the outer hull. The sound windows are advantageously formed in such a way that they form a soft transition and no edge with the outer hull.

In exemplary embodiments, the underwater sound receiving assembly can extend around a bow of the water vehicle. This is advantageous so that the sound incidence directions from which sound waves are detected are enlarged. Furthermore, the end fire beam, an adjustable receiving characteristic of the underwater sound assembly, is thus enabled not only for high-frequency signals, but also for lower-frequency signals. This is the case since the aperture of the underwater sound receiving assembly is enlarged.

Furthermore, a method for adapting the device for receiving underwater sound to the water vehicle is shown. The method comprises determining an acoustic impedance of the water vehicle. This can be carried out, for example, by means of the finite element method for a point grid in the installation space available in the water vehicle for the underwater sound receiving assembly. This is followed by the optimization of an arrangement of underwater sound receiving assemblies of the device for receiving underwater sound inside the available installation space in the water vehicle. The optimization comprises an analysis of the frequency response of the device for receiving underwater sound, wherein the frequency response is linearized by the optimization. In other words, in spite of the nonlinear shape of the underwater sound receiving assembly, in consideration of the behavior of the water vehicle on the incident sound waves, thus the acoustic impedance of the water vehicle, an approximation of the frequency response in the application range to a linear frequency response can take place.

To linearize the frequency response, the arrangement of the underwater sound receiving assembly can be varied. That is to say, the spacing between the underwater sound receiving assemblies or the underwater sound receivers and/or the spacing between sound reflectors and underwater sound receivers of the underwater sound assemblies and/or the size of the underwater sound receivers can be varied. Furthermore, the depth of the underwater sound receiving assembly, in particular of an underwater sound receiver, in the available installation space can

5 20216573_1 (GHMaters) P117465.AU also be varied. An optimization of one or more of the mentioned parameters can then result in improved linearization of the frequency response.

For a linear frequency response, the underwater sound receivers of the underwater sound receiving assembly are to be arranged at a spacing to one another such that in the observed frequency range, more precisely for a selected frequency, no maxima and minima result in the reception sensitivity. This is achieved when the underwater sound receivers are arranged at a spacing to one another which corresponds to half the wavelength of the selected frequency. In other words, the underwater sound receiving assembly is optimized for a selected frequency range by the selection of the spacings between the individual underwater sound receivers. Due to the optimization, the reception sensitivity of the underwater sound receiving assembly is (nearly) equal in the selected frequency range.

In exemplary embodiments, the underwater sound receiving assembly can be optimized not only for one frequency range, but for a plurality of frequency ranges. This is possible if groups of the underwater sound receivers are formed within the underwater sound receiving assembly. A first group of underwater sound receivers can thus be optimized for a first frequency range and a second group of underwater sound receivers can be optimized for a second frequency range. In the first group, the underwater sound receivers can have a first spacing to one another which corresponds to half the wavelength of a (center) frequency of the first frequency range and in the second group, the underwater sound receivers can have a second spacing to one another which corresponds to half the wavelength of a (center) frequency of the second frequency range.

This is advantageous to be able to monitor multiple frequency bands deliberately or to be able to suppress individual (dominant) frequencies. The suppression of frequencies can be reasonable if a loud sound source underwater is superimposed on a quiet sound source at a different frequency. The quiet sound source can then be detected using a group of underwater sound receivers if this group is optimized for a similar frequency and the loud frequencies of the other sound source have a corresponding spacing to the frequency (or the frequencies) of the quiet sound source.

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Preferred exemplary embodiments of the present invention are explained hereinafter with reference to the appended drawings.

4. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: shows a schematic illustration of the device for receiving underwater sound signals;

Figure 2: shows a schematic illustration of a water vehicle having the device from Figure 1 in a side view;

Figure 3: shows a schematic perspective illustration of the water vehicle from Figure 2; and

Figure 4: shows a schematic illustration of the water vehicle having a surface array of underwater sound receiving assemblies.

5. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Before exemplary embodiments of the present invention are explained in more detail below on the basis of the drawings, it is to be noted that identical, functionally equivalent, or identically acting elements, objects, and/or structures are provided with the same reference signs in the different figures, so that the description of these elements represented in different exemplary embodiments is exchangeable with one another or can be applied to one another.

Figure 1 shows a schematic illustration of a device 20 for receiving underwater sound. The device comprises a plurality of underwater sound assemblies 22a, 22b, 22c. The underwater sound assemblies 22 (each) have a sound window 24a, 24b, 24c, an underwater sound receiver 26a, 26b, 26c, and a sound reflector 28a, 28b, 28c. However, a common sound window can also be provided. The sound window associated with one of the underwater sound receiving assemblies is then a section of the common sound window, behind which the corresponding underwater sound receiver is arranged.

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The device is designed to receive sound waves which are incident (at least partially) from the y direction on the underwater sound assemblies. This direction is referred to as the sound incidence direction. Viewed from the sound incidence direction, the underwater sound receiver of an underwater sound assembly 22 is arranged between the associated sound window and the associated sound reflector. The sound reflector can be designed to bundle incident sound waves and focus them on the underwater sound receiver. For this purpose, the sound reflector can be made concave (in the direction of the underwater sound receiver). The sound window can be made convex on the side facing away from the underwater sound receiver. This increases the resistance to the water pressure. Furthermore, this can correspond to the shape of the outer hull of a water vehicle, so that the sound window is fitted to the shape of the outer hull. The sound window can also be made flat or planar, however, thus not convex.

The second underwater sound assembly 22b is arranged adjacent to the first underwater sound assembly 22a and to the third underwater sound assembly 22c. A spacing dl between the first and the second underwater sound assemblies 22a, 22b differs from a spacing d2 between the second and the third underwater sound assemblies 22b, 22c. In Figure 1, the spacing dl is less than the spacing d2. The spacing can be understood as the distance between the center points or centers of gravity of the underwater sound receivers.

Furthermore, a spacing d3, d4, d5 between the underwater sound receivers 26a, 26b, 26c and the corresponding sound reflectors 28a, 28b, 28c of the device can also vary. The design frequency of the individual underwater sound receiver assemblies can be adjusted via this spacing.

Furthermore, it is apparent that one underwater sound assembly, the third underwater sound assembly 22c here, is arranged offset to the rear in the sound incidence direction. The underwater sound receiving assemblies 22a, 22b, 22c are accordingly arranged on a curved line. The curved line has a curvature in the same direction in which the sound incidence direction also extends.

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Figure 2 shows a schematic illustration of a water vehicle 30 in a side view. The water vehicle 30 has an outer hull 32, which at least encloses a body of the water vehicle 30 where the water vehicle is in continuous contact with water in operation. An imaginary curved line 34 connects the underwater sound receiving assemblies, in particular the underwater sound receivers, to one another.

Figure 3 shows a schematic illustration of a detail of the bow of the water vehicle 30 from Figure 2 in a perspective illustration. It is clear here that the line 32 can be curved in the x and also in the y and in the z directions. The line can already experience a profile in three spatial directions in the event of two curvature changes. The device can therefore completely adapt itself to the shape of the outer hull of the water vehicle and even, as shown in Figure 3 with the underwater sound receiving assemblies 22c and 22d, can be laid around the bow of the water vehicle. No further underwater sound receiving assemblies are arranged on the bow of the water vehicle 30 between the underwater sound receiving assemblies 22c and 22d only for better illustration capability.

The design of the device, in particular the spacings dl to d5, the size of the underwater sound receivers 26a, 26b, 26c, can be specifically ascertained for each water vehicle. For example, this can take place on the basis of a (computer) model of the water vehicle in which, for example, the sound propagation is simulated by means of the finite element method. Optimization of the device to the water vehicle can be carried out by means of variation of the above-mentioned parameters. In particular, a frequency response of the device in an application range can thus be linearized. The application range can be between 1 and 100 kHz, in particular between 2 and 80 kHz. In addition to the possibility of changing a spatial arrangement of the underwater sound receiving assemblies or the underwater sound receivers, in order to linearize the frequency response, electronics which process the output signals of the underwater sound receivers can also linearize the frequency response, for example by means of delay elements.

In each of Figure 2 and Figure 3, only a line along which the underwater sound receiving assemblies can be arrayed is shown. A line array is thus formed. If further devices are arranged, for example, below the device shown in Figure 2 and Figure 3,

9 20216573_1 (GHMaters) P117465.AU lines arranged one below another result, along which underwater sound receiving assemblies can be arrayed (cf. Figure 4). A surface array is then formed. In particular to be able to adapt the surface array to the outer hull of the water vehicle, however, the lines typically do not extend in parallel. That is to say that spacings between adjacent underwater sound receiving assemblies arranged on different lines can vary.

Thus, Figure 4 shows a schematic illustration of the water vehicle 30. Three lines 32, 32', and 32" are shown, on which the underwater sound assemblies 22a, 22b, 22c, 22a', 22b', 22c', 22a", 22b", 22c" are arranged. The underwater sound assemblies form a 3 x 3 array.

Although some aspects have been described in the context of a device, it is clear that these aspects also represent a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Similarly thereto, aspects which were described in the context of or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.

Depending on specific implementation requirements, exemplary embodiments of the invention can be implemented in hardware or in software. The implementation can be carried out using a digital storage medium, for example a diskette, a DVD, a Blu-ray disc, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, a hard drive or another magnetic or optical memory, on which electronically readable control signals are stored, which can interact or which interact with a programmable computer system so that the respective method is carried out. The digital storage medium can therefore be computer readable. Some exemplary embodiments according to the invention thus comprise a data carrier having electronically-readable control signals which can interact with a programmable computer system so that one of the methods described herein is carried out.

In general, exemplary embodiments of the present invention can be implemented as a computer program product having a program code, wherein the program code acts to execute one of the methods when the computer program product runs on a

10 20216573_1 (GHMaters) P117465.AU computer. The program code can also be stored, for example, on a machine readable carrier. Other exemplary embodiments comprise the computer program for carrying out one of the methods described herein, wherein the computer program is stored on a machine-readable carrier.

In other words, one exemplary embodiment of the method according to the invention is therefore a computer program which has a program code for carrying out one of the methods described herein when the computer program runs on a computer. A further exemplary embodiment of the methods according to the invention is therefore a data carrier (or a digital storage medium or a computer-readable medium), on which the computer program for carrying out one of the methods described herein is recorded.

A further exemplary embodiment of the method according to the invention is therefore a data stream or a sequence of signals which represents the computer program for carrying out one of the methods described herein. The data stream or the sequence of signals can be configured, for example, to be transmitted via a data communication connection, for example via the Internet.

A further exemplary embodiment comprises a processing device, for example a computer or a programmable logic device, which is configured or adapted to carry out one of the methods described herein.

A further exemplary embodiment comprises a computer on which the computer program for executing one of the methods described herein is installed.

In some exemplary embodiments, a programmable logic device (for example a field programmable gate array (FPGA)) can be used to execute some or all functionalities of the methods described herein. In some exemplary embodiments, a field programmable gate array can cooperate with a microprocessor to carry out one of the methods described herein. In general, the methods in some exemplary embodiments are carried out on the part of any hardware device. This can be universally usable hardware such as a computer processor (CPU) or hardware specific for the method, for example an ASIC.

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The above-described exemplary embodiments merely represent an illustration of the principles of the present invention. It is obvious that modifications and variations of the arrangements and details described herein will be apparent to other persons skilled in the art. It is therefore intended that the invention is solely restricted by the scope of protection of the following patent claims and not by the specific details which were presented on the basis of the description and the explanation of the exemplary embodiments herein.

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List of reference numerals:

20 device 22 underwater sound receiving assembly 24 sound window 26 underwater sound receiver 28 sound reflector 30 water vehicle 32 outer hull 34 line

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Claims

Patent claims

1. An array arrangement comprising a plurality of underwater sound receiving assemblies, for receiving underwater sound, wherein the plurality of underwater sound receiving assemblies each form an individual module that has an underwater sound receiver, a sound reflector and a sound window or a common sound window; wherein a first one of the underwater sound receiving assemblies is arranged adjacent to a second one of the underwater sound receiving assemblies and wherein a third one of the underwater sound receiving assemblies is arranged adjacent to the second underwater sound receiving assembly; wherein the first and the second underwater sound receiving assemblies have a first spacing to one another and wherein the second and the third underwater sound receiving assemblies have a second spacing to one another, wherein the first and the second spacings differ from one another, wherein the underwater sound receiving assemblies are arranged in a chamber behind the sound window or common sound window, the chamber being filled with water, and wherein the common sound window or the sound windows of the sound receiving assemblies allow a water exchange between water surrounding the array arrangement and the water in the chamber.

2. The array arrangement as claimed in claim 1, wherein the individual modules of underwater sound receiving assemblies are arrayed along a curved line.

3. The array arrangement as claimed in claim 2, wherein the line has a curvature in a first direction and in a second direction.

4. The array arrangement as claimed in claim 3, wherein the line has a profile in three spatial directions due to the curvature in the first direction and the second direction.

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5. The array arrangement as claimed in claim 1, wherein the individual modules of underwater sound receiving assemblies are arrayed along a plurality of curved lines.

6. The array arrangement as claimed in claim 1, wherein the plurality of curved lines have a curvature in a first direction and in a second direction.

7. The array arrangement as claimed in claim 6, wherein the plurality of curved lines have a profile in three spatial directions due to the curvature in the first direction and the second direction.

8. The array arrangement as claimed in claim 7, wherein adjacent ones of the plurality of curved lines do not have an equidistant spacing.

9. The array arrangement as claimed in any one of the preceding claims, wherein a size of the underwater sound receivers of the plurality of underwater sound receiving assemblies differs from one another.

10. The array arrangement as claimed in any one of the preceding claims, wherein a spacing of the underwater sound receiver from the sound reflector of the plurality of underwater sound receiving assemblies differs from one another.

11. A water vehicle, comprising: a body which is delimited by an outer hull, wherein the outer hull is designed to be in contact with surrounding water; and an array arrangement as claimed in any one of claims 1 to 10, wherein the plurality of modular underwater sound receiving assemblies are installed in the water vehicle in such a way that the respective sound windows enable the incidence of a sound wave in the body, wherein the associated underwater sound receivers are arranged in the body between the sound windows and the associated sound reflectors; wherein the underwater sound receiving assemblies are arranged in a chamber behind the respective sound windows, the chamber being filled with water, and

15 20216573_1 (GHMaters) P117465.AU wherein the outer hull, the common sound window or the respective sound windows allow a water exchange of the water surrounding the water vehicle with the water in the chamber.

12. The water vehicle as claimed in claim 11, wherein the sound windows close an opening of the outer hull.

13. The water vehicle as claimed in either one of claims 11 and 12, wherein the sound windows terminate with the outer hull.

14. The water vehicle as claimed in any one of claims 11 to 13, wherein the array arrangement of underwater sound receiving assemblies extends around a bow of the water vehicle.

15. A method for adapting an array arrangement for receiving underwater sound in accordance with any one of claims 1 to 10 to a water vehicle, the method having the following steps: determining an acoustic impedance of the water vehicle; and optimizing the array arrangement of the modular underwater sound receiving assemblies for receiving the underwater sound inside an available installation space in the water vehicle.

16. The method as claimed in claim 15, wherein the optimizing step comprises an analysis of the frequency response of the array arrangement, wherein the frequency response is linearized by the optimization.

17. The method as claimed in either one of claims 15 and 16, wherein the array arrangement of the modular underwater sound receiving assemblies comprises a spacing between the plurality of underwater sound receiving assemblies and/or a spacing between the sound reflectors and the underwater sound receivers of the plurality of underwater sound assemblies and/or a size of the underwater sound receivers.

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