Method for determining the location of sound-emitting underwater objects

Abstract

The present invention relates to methods for determining the location of underwater objects that emit sounds. The present solution can be used for determining the position and movement of different objects that emit sounds, such as marine mammals, underwater vessels, sources of geological noise, and other sources of sounds of a biological, geological or technological nature. According to the invention, two channels are formed on each hydroacoustic receiver: in the first channel, a digitized signal from an underwater entity is recorded; in the second channel on each hydroacoustic receiver, time signals from a receiver of a global navigation satellite system are recorded. In the first channel on each hydroacoustic receiver, signatures of interest are isolated, and the isolated signatures on recordings made using different recording points are compared. The technical result is that of obviating the need for a constant connection between spaced-apart hydroacoustic receivers.

Description

[0001] METHOD FOR DETERMINING THE LOCATION OF UNDERWATER OBJECTS EMISSIONS OF SOUND

[0002] The field of technology to which the invention relates.

[0003] This invention relates to methods for determining the location of underwater objects emitting sounds, which uses at least two spaced hydroacoustic receivers, with the help of which an analog signal from an underwater object emitting sounds is recorded on each hydroacoustic receiver. This solution can be used to determine the location and movements of various underwater objects emitting sounds: marine mammals, underwater vehicles, sources of geological noise, and other sources of sounds of biological, geological and man-made nature.

[0004] The following terms are used in this description:

[0005] Equalization is a frequency correction of sound. That is, the principle of equalization is to lower or raise the volume level of certain frequencies.

[0006] A signature is the minimum characteristic part of a sound signal sufficient to identify a sound source, or its representation in one form or another.

[0007] Time synchronization methods:

[0008] GPS (Global Positioning System) - Global Positioning System. Time synchronization is performed during the determination of the location of a device equipped with a GPS receiver. To do this, the device receives a signal from satellites installed in near-earth orbit. Each of the satellites has an atomic clock, due to which the GPS system provides good accuracy. The disadvantage of this method is the need for a GPS antenna, the signal from which can be unstable.

[0009] 1 PPS (1 pulse per second) - The 1 PPS signal does not contain a time stamp. The Master device sends 1 pulse per second over a separate network: fiber optic line, twisted pair, or coaxial cable. The Slave clock uses this pulse only to synchronize the beginning of each second. Devices cannot obtain date and time information using 1 PPS, so it is most often used in conjunction with other synchronization protocols.

[0010] State of the art.

[0011] There are methods for determining the location of underwater objects emitting sounds, for example, the invention "Method for determining the location of objects in a passive monitoring system" is known, Russian Federation patent No. 2526896, IPC G01 S 15 / 004, which uses at least two spaced hydroacoustic receivers, including a signal digitization unit, a power source and a long-term data storage unit, using said hydroacoustic receivers to record an analog signal from an underwater object emitting sounds on each hydroacoustic receiver, converting the analog signal into a digital one, forming the first recording channel on each hydroacoustic receiver.

[0012] This method is the closest in technical essence and achievable technical result and is chosen as the prototype of the proposed invention.

[0013] The disadvantages of this method include the need for constant communication between spaced receivers, implemented, for example, using a cable or a radio channel.

[0014] Disclosure of invention.

[0015] Based on this original observation, the present invention is primarily aimed at proposing a method for determining the location of underwater objects emitting sounds, which makes it possible to at least mitigate at least one of the above-mentioned disadvantages, namely, to ensure the absence of the need for constant communication between spaced hydroacoustic receivers, which is the objective of the present invention.

[0016] To achieve this goal, the method for determining the location of underwater objects emitting sounds is essentially characterized by the fact that the method additionally includes the following steps:

[0017] • two channels are formed on each hydroacoustic receiver, the first channel records the digitized signal from the underwater object, • the second channel on each hydroacoustic receiver records the precise time signals from the receiver of the global navigation satellite system, in which a specialized 1 PPS signal is allocated, synchronized with the general clock, and metadata, including the geographic location - longitude and latitude - of the registration point,

[0018] • in the first channel on each hydroacoustic receiver, the signatures of interest are selected,

[0019] • compare the selected signatures on the records made using different registration points,

[0020] • determine the location of an underwater object emitting sounds based on the geographic location of the recording points using the range difference method based on the coincidence of the selected signatures from different hydroacoustic receivers.

[0021] These advantageous characteristics make it possible to determine the location of underwater objects by determining the correspondence of signatures on records made using different recording points without the need for constant communication between spaced hydroacoustic receivers.

[0022] There is a variant of the invention in which metadata is recorded in the second channel on each hydroacoustic receiver using one of the modulation methods that is resistant to various methods of audio data compression and equalization.

[0023] These advantageous characteristics make it possible to compress and equalize audio data.

[0024] There is another variant of the invention, in which data from hydroacoustic receivers is transmitted to a control system, which includes a computing module that provides automatic detection of the required signatures.

[0025] These advantageous characteristics make it possible to automatically detect the required signatures.

[0026] There is also a variant of the invention, in which the control system transmits either the signature identifier and metadata, or a dedicated piece of signal, via radio or cable, i.e. at least two channels - signal and metadata. Due to these advantageous characteristics, it becomes possible to conduct long-term monitoring of water areas, track the appearance and movement of underwater sound sources (marine mammals, various geological and man-made sources), both in post-processing and in real time, depending on the system configuration. The number of recording points is not limited in any way and allows building various monitoring systems taking into account the specifics of a particular area.

[0027] The set of essential features of the proposed invention is unknown from the state of the art for methods of similar purpose, which allows us to conclude that the invention meets the criterion of "novelty" in relation to the method. In addition, this solution is not obvious to a specialist in this field.

[0028] Brief description of the drawings.

[0029] Other distinctive features and advantages of the present invention are clearly evident from the description given below for illustration and not as limiting, with reference to the accompanying drawings, in which:

[0030] - figure 1 depicts a general diagram of recording metadata according to the invention,

[0031] - figure 2 depicts a fragment of a two-channel recording of an audio signal (upper channel) and metadata (lower channel), according to the invention,

[0032] - Figure 3 shows a fragment of the record on a larger scale, where two adjacent metadata records can be seen, according to the invention.

[0033] Figure 1 shows the general scheme of recording metadata: the internal clock of the recording unit records the moment of occurrence of the 1 PPS signal from the receiver of the satellite navigation system, and the actual recording of data in the additional channel is carried out after the period of the exact time signal (1 second), since during this second the receiver transmits navigation data, and the recording unit decodes them.

[0034] Figure 2 shows a fragment of the recording, where the upper channel shows the signal from the hydroacoustic receiver, and the lower channel shows metadata (geographical position data recorded synchronously with the 1 PPS signal using frequency manipulation). Figure 3 shows a fragment of the recording on a larger scale, where two adjacent metadata records can be seen.

[0035] In addition, the registration point may contain a computing module that provides automatic detection of the required signatures, and a communication module (including satellite), by means of which the part of the recording of interest with time reference is automatically or on demand transmitted to the control system. When the control system receives such parts from different registration points, it determines the location of the sound source.

[0036] The registration point contains an array of sound receivers (hydroacoustic receivers, microphones), and the number of channels in the digital recording at least corresponds to the number of receivers plus one, in which at least time marks are recorded. Also, the geographic location of the reception point, the orientation of the array of receivers relative to the cardinal points and / or horizontal, for which the registration point is equipped with a heading sensor and a horizontal (vertical) sensor, can be recorded in an additional channel as metadata.

[0037] Implementation of the invention.

[0038] The method for determining the location of underwater objects emitting sounds works as follows. Let us give the most comprehensive example of the invention implementation. Bearing in mind that this example does not limit the application of the invention.

[0039] Stage 1. In parallel with the digital recording of the sound analog signal received from the hydroacoustic receiver (or microphone) into the first channel, precise time signals from the GNSS (Global Navigation Satellite System) receiver are recorded into the second channel.

[0040] Step 2: GNSS receivers have a dedicated 1 PPS signal, synchronized to the overall system clock with an accuracy of about 20 ns in modern receivers and transmitted at a frequency of 1 Hz.

[0041] Step 3: A 1 PPS signal is emitted by the navigation receiver at the start of each second, after which the receivers typically transmit the generated navigation data.

[0042] Stage 4. Metadata is recorded in the second audio channel using one of the modulation methods that is resistant to various methods of audio data compression and equalization (compression, volume change, bit depth, etc.), for example, using frequency shift keying (FSK). Stage 5. The problem of determining the geographic location of underwater objects emitting sounds is solved, for which, in addition to precise time reference, at least the latitude and longitude of the recording point are used.

[0043] Industrial applicability.

[0044] The proposed method for determining the location of underwater objects emitting sounds can be implemented by a specialist in practice and, when implemented, ensures the implementation of the stated purpose, which allows us to conclude that the invention meets the “industrial applicability” criterion.

[0045] In accordance with the proposed invention, a method for determining the location of underwater objects emitting sounds was tested.

[0046] Tests have shown that the method makes it possible to eliminate the need for constant communication between spaced hydroacoustic receivers.

[0047] An additional useful technical result of the claimed invention is that universalization is achieved: since a signal is simply recorded into an audio file, it can be processed by standard means, stored, transmitted, etc., like ordinary sound.

Claims

CLAUSES OF THE INVENTION 1. A method for determining the location of underwater objects emitting sounds, in which • use at least two spaced hydroacoustic receivers, including a signal digitization unit, a power source and a long-term data storage unit, • using the specified hydroacoustic receivers, an analog signal is recorded from an underwater object emitting sounds to each hydroacoustic receiver, • convert the analog signal into digital, forming the first recording channel on each hydroacoustic receiver, • characterized in that • two channels are formed on each hydroacoustic receiver, and the digitized signal from the underwater object is recorded in the first channel, • the second channel on each hydroacoustic receiver records precise time signals from a global navigation satellite system receiver, in which a specialized 1 PPS signal is allocated, synchronized with the general clock, and metadata, including the geographic location - longitude and latitude - of the registration point, • in the first channel on each hydroacoustic receiver, the signatures of interest are identified, • compare the selected signatures on the recordings made using different registration points, • determine the location of an underwater object emitting sounds based on the geographic location of the recording points using the range difference method based on the coincidence of the selected signatures from different hydroacoustic receivers.

2. The method according to paragraph 1, characterized in that metadata is recorded in the second channel on each hydroacoustic receiver using one of the modulation methods that is resistant to different methods of audio data compression and equalization.

3. The method according to paragraph 1, characterized in that the data from the hydroacoustic receivers is transmitted to the control system, which includes a computing module that provides automatic detection of the required signatures.

4. The method according to paragraph 3, characterized in that the control system transmits via radio or cable either the signature identifier and metadata, or a selected portion of the signal, that is, at least two channels - a signal and metadata.

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