JP2018146353A - Sonar device, acoustic signal processing system, acoustic signal processing method, and acoustic signal processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sonar device, an acoustic signal processing system, an acoustic signal processing method, and an acoustic signal processing program that can accurately calculate an arriving direction of an acoustic signal radiated by an underwater vehicle by using a simple configuration.SOLUTION: A sonar device includes: at least one S/N ratio calculation unit configured to calculate an S/N ratio of an acoustic signal received by an acoustic sensor; at least one integration processing unit configured to perform an integration process of the acoustic signal over a set integration time; at least one integration time selection unit configured to select the integration time on the basis of the S/N ratio; and at least one direction calculation unit configured to calculate the direction of the received acoustic signal on the basis of the at least one acoustic signal integrated over the selected integration time.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sonar device, an acoustic signal processing system, an acoustic signal processing method, and an acoustic signal processing program.

  For ships, underwater vehicles for military purposes that cannot be detected by radar devices or optical sensors that use radio waves are a major threat. In order to detect a submerged underwater vehicle, a method of detecting an acoustic signal (sound wave) emitted from the underwater vehicle by dropping an acoustic sensor from an aircraft into the sea is effective.

  The sonar device detects an acoustic signal emitted from the underwater vehicle and calculates the position of the underwater vehicle. In a sonar device, in order to improve the S / N ratio by separating weak underwater sound waves and underwater noise radiated from the underwater vehicle, there are many cases where long-time integration processing as shown in FIG. 6 is performed.

  Patent Document 1 discloses a signal source orientation estimation method using a sensor array in which a plurality of acoustic sensors are arranged in an array. According to the method of Patent Document 1, it is observed that the time change rate of the direction of the underwater vehicle observed with the acoustic sensor increases as the underwater vehicle approaches the acoustic sensor. The optimal integration time of the acoustic signal is determined based on the rate of change.

JP 2006-078331 A

  The disclosure of the above document is incorporated herein by reference. The analysis of the related technology described above is given below.

  However, long-time integration processing of the received acoustic signal causes a delay in output timing of the processing result. As a result, as illustrated in FIG. 7, an azimuth calculation error increases at a position where the underwater vehicle is closest to the acoustic sensor and in the vicinity thereof.

  In addition, the integration process in the azimuth calculation disclosed in Patent Document 1 is performed after the optimum integration time is determined. As a result, the integration process is affected by the acoustic signal received in the past, and this causes a problem that the accuracy of the azimuth calculation is lowered.

  The present invention has been made in view of the above problems, and one of its purposes is to accurately calculate the arrival direction of an acoustic signal radiated from an underwater vehicle using a simple configuration. To provide a sonar device, an acoustic signal processing system, an acoustic signal processing method, and an acoustic signal processing program. Other objects and advantages will be apparent to those skilled in the art from this disclosure.

  According to one aspect of the present invention, at least one S / N ratio calculator configured to calculate an S / N ratio of an acoustic signal received by an acoustic sensor, and an integration time set with the acoustic signal. And at least one integration processing unit configured to select the integration time based on the S / N ratio, and the selected integration time. And a sonar device having at least one orientation calculator configured to calculate an orientation of the received acoustic signal based on the integrated at least one acoustic signal.

  According to one aspect of the present invention, there is provided an acoustic signal processing system including the sonar device and the acoustic sensor described above, wherein the acoustic sensor is mounted on a ship or towed by a ship.

  According to one aspect of the present invention, an S / N ratio of an acoustic signal received by an acoustic sensor is calculated, the acoustic signal is integrated with a set integration time, and the acoustic signal is integrated based on the S / N ratio. An acoustic signal processing method is provided for selecting an integration time and calculating an orientation of the received acoustic signal based on at least one of the acoustic signals integrated with the selected integration time.

  According to one aspect of the present invention, a function of calculating an S / N ratio of an acoustic signal received by an acoustic sensor, a function of integrating the acoustic signal with a set integration time, and the S / N ratio. A sound for causing a computer to execute a function of selecting the integration time based on the sound and a function of calculating a direction of the sound signal received based on the at least one sound signal integrated with the selected integration time. A signal processing program is provided.

  According to one aspect of the present invention, the S / N ratio is calculated based on a plurality of acoustic signals received by an acoustic sensor and having at least one of integration processing presence / absence, integration time, sampling period, and sampling frequency. An acoustic signal processing program for causing a computer to execute the function to perform is provided.

  In addition, a computer-readable recording medium (for example, a hard disk drive (HDD), a compact disk (CD) / DVD (digital versatile disk), a non-transitory computer readable recording medium such as a semiconductor storage device) that stores the above-described program or the like. Provided.

  According to one aspect of the present invention, a sonar device, an acoustic signal processing system, an acoustic signal processing method, and an acoustic signal that can accurately calculate the arrival direction of an acoustic signal emitted by an underwater vehicle using a simple configuration. A signal processing program can be provided.

It is a figure for demonstrating the outline | summary of the system which detects the acoustic signal which an underwater vehicle radiates | emits, and calculates the direction of an underwater vehicle. It is a block diagram for demonstrating the structure of the sonar apparatus which concerns on 1st Embodiment applicable to the system shown in FIG. FIG. 3 is a block diagram of the sonar device shown in FIG. 2 including an integration time selection unit. It is a figure for demonstrating an example of a S / N ratio calculation algorithm. It is a figure for demonstrating the relationship between a sound wave propagation distance and the sound pressure level of the underwater sound wave which the underwater navigation body which an acoustic sensor receives. It is a figure for demonstrating the improvement effect of the estimated azimuth | direction precision by integrating the underwater sound wave which an underwater vehicle radiates | emits. The time change of the direction calculation error when the integration time is relatively long is shown. The time change of the direction calculation error when the integration process is not performed is shown. The azimuth | direction calculation error at the time of changing integration time according to the result of the S / N ratio calculation process of an input signal according to 1st Embodiment is shown. It is a figure for demonstrating the outline | summary of the other system which calculates the direction of an underwater vehicle using a towed acoustic sensor. It is a figure explaining the basic concept of the sonar apparatus which concerns on one Embodiment.

  With reference to FIG. 11, the basic concept of the sonar apparatus of one Embodiment is demonstrated. The sonar device 1101 includes at least one S / N ratio calculation unit 1102, at least one integration processing unit 1103, at least one integration time selection unit 1104, and at least one azimuth calculation unit 1105. Each of the units 1102 to 1105 can be configured by software, hardware, or a combination thereof, alone or in combination.

  The timing chart shown in FIG. 11 is illustrated to show an example of the operation of the sonar device 1101, and is not described with the intention of specifying the operation of the sonar device 1101. As will be described later with reference to FIG. 4, the sonar device can perform various operations.

  At least one S / N ratio calculation unit 1102 is configured to calculate the S / N ratio of the acoustic signal received by the acoustic sensor (see the acoustic sensor 3 in FIG. 1 or the towed acoustic sensor 23 in FIG. 10). .

  At least one integration processing unit 1103 is configured to integrate the acoustic signal with a set integration time.

  At least one integration time selection unit 1104 is configured to select an integration time based on the S / N ratio.

  The azimuth calculation unit 1105 is configured to calculate the azimuth of the received acoustic signal based on at least one acoustic signal (for example, acoustic signal components in the X-axis and Y-axis directions) integrated with the selected integration time.

  According to the sonar device 1101, an S / N ratio calculation unit 1102 (see the S / N ratio calculation unit 13 in FIGS. 2 to 4) and an integration time selection unit 1104 (an integration time selection unit 15 in FIG. 3) are added. The azimuth calculation accuracy is improved.

  According to the sonar device 1101, after obtaining a plurality of integration processing results having different integration times (time constants) in advance, an optimum integration time value is determined, and the optimum integration time is selected from the plurality of integration processing results. It is possible to extract the optimum integration processing result processed in the above. For this reason, after the optimum integration time is determined, the optimum integration processing result can be immediately extracted without calculating the azimuth change or the like. The optimum integration time can be determined according to the S / N ratio of the received acoustic signal. For example, the integration time may be optimized as the S / N ratio of the acoustic signal radiated from the underwater vehicle received by the acoustic sensor increases with the proximity of the underwater vehicle.

  According to the determination of the optimum integration time based on the S / N ratio, the optimization of the integration time is performed more quickly than the determination of the integration time based on the change in direction of the underwater vehicle. Therefore, according to the sonar device 1101, the direction calculation accuracy when calculating the arrival direction of the acoustic signal radiated from the underwater vehicle is improved. This improves the performance of identifying the position of the underwater vehicle.

  The acoustic signal processing method described above works effectively even when the sonar device 1101 has one acoustic sensor, and also works effectively when the sonar device 1101 uses an acoustic sensor that is towed by a ship.

  On the other hand, according to the method of Patent Document 1 described above, after calculating the azimuth change of the acoustic signal emitted by the underwater vehicle, the optimum integration time of the received acoustic signal is determined based on this azimuth change. Then, the integration process of the received acoustic signal is executed with the integration time determined after the determination.

  According to the method of Patent Literature 1, since the integration process optimized after calculating the azimuth change is executed, it takes time until the integration process is optimized, and the acoustic signal received in the past by the integration process There is a problem of being affected. For this reason, according to the method of patent document 1, there exists a problem that the estimation precision of the direction of an underwater vehicle is low.

<Embodiment>
Exemplary embodiments of the present invention will be described with reference to the drawings.

  The sonar device according to the embodiment can use an acoustic sensor that is installed in a sea area where an underwater vehicle is expected to exist using a ship or an aircraft. The sonar device can calculate an azimuth of the underwater vehicle by detecting an acoustic signal radiated (including reflection) by the underwater vehicle.

<First Embodiment>
FIG. 1 is a diagram for explaining an outline of a system that detects an acoustic signal radiated from an underwater vehicle and calculates an orientation of the underwater vehicle.

  In FIG. 1, a passing course 2 indicates the course of the underwater vehicle 1. In this embodiment, the acoustic sensor 3 is a reception-only acoustic sensor that does not transmit an acoustic signal and receives an acoustic signal emitted from the underwater vehicle, but is not limited thereto. The closest position 4 is a position where the underwater vehicle 1 is closest to the acoustic sensor 3. The closest approach distance 5 is the closest approach distance between the underwater vehicle 1 and the acoustic sensor 3, and is, for example, 1 km. The sound wave propagation distance 6 is a distance until the acoustic signal radiated from the underwater vehicle 1 reaches the acoustic sensor 3, and is 30 km, for example. The sound wave arrival direction 7 indicates the arrival direction of the acoustic signal emitted from the underwater vehicle 1 as viewed from the acoustic sensor 3.

  FIG. 2 is a block diagram for explaining the configuration of the sonar device according to the first embodiment applicable to the system shown in FIG. The upper part of FIG. 2 shows a configuration for processing a component in the Y-axis direction, and the lower part of FIG. 2 shows a configuration for processing a component in the X-axis direction. 3 is a block diagram of the sonar device shown in FIG. 2 including an integration time selection unit. The upper part of FIG. 3 shows a configuration for processing the component in the Y-axis direction, and the lower part of FIG. 2 shows a configuration for processing the component in the X-axis direction.

  Referring to FIG. 2, the sonar device according to the first embodiment includes the acoustic sensor 3 as shown in FIG. The acoustic sensor 3 incorporates two piezoelectric ceramics (not shown) having directivity on the X axis and Y axis orthogonal to the horizontal direction, that is, the X axis directivity 9 and the Y axis directivity 8. The sonar device can calculate the direction of arrival of the acoustic signal based on the difference in the received sound pressure level between the two piezoelectric ceramics (see Japanese Patent Application Laid-Open No. 60-205269).

  Further, the sonar device includes a low pass filter (hereinafter abbreviated as “LPF”) 10, analog / digital in a configuration for processing a component in the Y-axis direction and a configuration for processing a component in the X-axis direction. Signal converter (hereinafter abbreviated as “A / D converter”) 11, Fast Fourier Transform processor (hereinafter abbreviated as “FFT processor”) 12, signal to noise ratio calculator (hereinafter “S / N ratio calculation”) Each of which has an integration processing unit 14, an integration time selection unit 15 (see FIG. 3), and an azimuth calculation unit 16.

  Next, the outline | summary of each part 10-16 is demonstrated.

  In the configuration for processing the component in the Y-axis direction, the acoustic sensor 3 outputs a signal based on the received acoustic signal. The output of the acoustic sensor 3 is directly or indirectly connected to the input of the LPF 10. The output of the LPF 10 is directly or indirectly connected to the input of the A / D converter 11. The output of the A / D conversion unit 11 is directly or indirectly connected to the input of the FFT processing unit 12. The output of the FFT processing unit 12 is directly or indirectly connected to the input of the S / N ratio calculation unit 13 and the input of the integration processing unit 14.

  The integration processing unit 14 can include a plurality of integration processing units 14. The plurality of integration processing units 14 can perform integration processing of acoustic signals with different integration times and output integrated signals, respectively. Alternatively, the integration processing unit 14 may be configured to output an integration result every elapse of a predetermined period.

  The output of the S / N ratio calculation unit 13 and the output of the integration processing unit 14 are directly or indirectly connected to the input of the integration time selection unit 15. The integration time selection unit 15 uses the output signal of the S / N ratio calculation unit 13 as a control signal, selects at least one of a plurality of signals output by the integration processing unit 14 and outputs the selected signal to the direction calculation unit 16 To do.

  The outline of the configuration for processing the component in the Y-axis direction has been described above, but the same applies to the configuration for processing the component in the X-axis direction. It should be noted that the integration time selection unit 15 may be shared with respect to the Y-axis direction and the X-axis direction, or may be separated according to circumstances.

  Next, the process in each part 10-16 is demonstrated concretely.

  The LPF 10 removes a high-frequency component that is 1/2 or more of the sampling frequency of the A / D converter 11 in the subsequent stage from the analog signal of the input acoustic signal (underwater acoustic wave).

  The A / D converter 11 converts the analog signal of the acoustic signal into a digital signal.

  The FFT processing unit 12 decomposes the digital signal of the acoustic signal into frequency components using a fast Fourier transform algorithm. By decomposing the underwater sound wave signal into frequency components by FFT processing, the underwater sound wave signal is composed of a frequency component including an underwater vehicle radiated sound wave, which is an artificial underwater sound wave, and a natural underwater noise. And can be separated. This improves the S / N ratio.

  The S / N ratio calculation unit 13 calculates the S / N ratio of the digital signal of the acoustic signal. Examples of the S / N ratio calculation algorithm used by the S / N ratio calculation unit 13 include a processing method called “noise average” as disclosed in Japanese Patent Laid-Open No. 60-205269, or Japanese Patent Laid-Open No. 2013-2013. The calculation method of the S / N ratio using the directivity of the acoustic sensor as disclosed in Japanese Patent No. 160564 can be used, but is not limited to these, and the S / N as shown in FIG. An N ratio calculation algorithm can also be used.

  The integration processing unit 14 integrates the data signal of the sound pressure level decomposed for each frequency component by the FFT processing for a set time. Thereby, the S / N ratio of the acoustic signal can be improved. The integration process is executed for the number of outputs of the FFT process. This integration process has the effect of improving the S / N ratio of the acoustic signal before the azimuth calculation process.

  However, a long integration process causes an output delay of the processing result. With reference to FIG. 1, the processing output delay due to the integration time increases the error in the estimated azimuth particularly when the underwater vehicle 1 and the acoustic sensor 3 are closest to each other. In order to eliminate this, an integration time selection unit 15 is provided in the present embodiment.

  The integration processing unit 14 may include a plurality of integrators having different time constants (for example, 2, 4,..., 128 seconds). Alternatively, the integration processing unit 14 may be configured to store sampled data and perform integration processing or the like on the sampled data in response to a command.

  The integration time selection unit 15 selects an integration time used for the subsequent azimuth calculation according to the result of the S / N ratio calculation of the acoustic signal so that a signal with an optimized S / N ratio is output. To.

  The azimuth calculation unit 16 calculates the azimuth of arrival of the acoustic signal based on the received sound pressure level difference between the signal with the Y-axis directionality 8 and the signal with the X-axis directionality 9 whose S / N ratio is optimized. To do.

<New S / N ratio calculation algorithm>
FIG. 4 shows a new S / N ratio calculation algorithm that can be used by the S / N ratio calculation unit 13 shown in FIG.

In general, the longer the integration time, the better the S / N ratio of an underwater noise level having a 1 / f fluctuation component peculiar to the natural world in proportion to the square root of the integration time. Therefore, an output value obtained by integrating the input signal with an integration time of M seconds (for example, a value obtained by integrating data output in a 1-second cycle M times and divided by M), and an output value when the input signal is not integrated This relationship can be expressed by the following equation, where S is the level of an artificial signal sound and N is the underwater noise level.
S / N ratio without integration = S ÷ (S + N)
S / N ratio integrated M times = S ÷ (S + N × SQRT (M))
Assuming that S ÷ (S + N) is constant, the following proportional relationship is obtained.
“No integration”: “M second integration” = 1 ÷ (1 × M): 1 ÷ (1 × SQRT (M))
“No integration” × 1 ÷ (SQRT (M)) = “M second integration” × 1 ÷ M
"No integration" x M = "M second integration" x SQRT (M)
Therefore, the output value of “no integration” is SQRT (M) ÷ M times “M second integration”.

  That is, the underwater noise level for the input signal (“no integration”) can be expressed as:

  Underwater noise level = ("No integration"-"M second integration") / (1-SQRT (M) / M)

  Therefore, the level of the underwater noise component can be estimated from the difference between the input data without integration processing and with the integration processing and the integration time (number of integrations). Based on the level of this noise component, the optimum integration time, in other words, the integration period, the number of samplings, or the sampling period (the product of the number of samplings and the sampling period) can be determined. As a result, optimum data is output from a plurality of data obtained by the integration processing that has been processed in parallel with the S / N ratio calculation. Alternatively, stored data for the optimized number of samplings may be integrated and data divided by the number of samplings may be output.

  Note that if the integration time (M seconds) for calculating the underwater noise level is long, the change in the S / N ratio due to the change in the distance between the underwater vehicle 1 and the acoustic sensor 3 cannot be ignored. For example, it may be 16 seconds or less.

  Here, an example of setting the integration time M when the underwater vehicle 1 is closest to the acoustic sensor 3 (see the closest position 4 in FIG. 1) will be described. When the underwater vehicle 1 is present near the closest position 4, the relative change in the sound wave propagation distance 6 (see FIG. 1) per time is large. Therefore, the change in the S / N ratio of the received acoustic signal also increases. Therefore, in the S / N ratio calculation algorithm shown in FIG. 4, if the value of the integration time (number of integrations) M is increased, the S / N ratio calculation error may increase. Therefore, an appropriate value for the integration time M is about 16 to 32.

  Next, the direction calculation of the underwater vehicle using the sonar device described with reference to FIGS. 1 to 4 will be described with reference to FIGS.

  As an example, the speed of the underwater vehicle 1 is 30 km / h, and the underwater vehicle 1 is moved away from the acoustic sensor 3 (the sound wave propagation distance 6 is 30 km) from the distance (the closest distance 5 is 1 km) and separated (the sound wave propagation). Assuming a situation in which the distance 6 is 30 km), the azimuth of the underwater vehicle 1 was calculated using the S / N ratio calculation algorithm shown in FIG.

  FIG. 5 is a diagram for explaining the relationship between the sound wave propagation distance 6 and the sound pressure level of the underwater sound wave (acoustic signal) emitted by the underwater vehicle 1 received by the acoustic sensor 3. In FIG. 5, the solid line indicates the time change of the sound wave propagation distance 6 until the sound wave emitted from the underwater vehicle 1 reaches the acoustic sensor 3. Since the underwater vehicle 1 approaches the acoustic sensor 3 at a speed of 30 km / h from a point at a distance of 30 km, the time required for the underwater vehicle 1 to reach the closest position 4 is 60 minutes.

  In FIG. 5, the dotted line indicates that the S / N ratio 17 (corresponding to the output signal of the S / N ratio calculator 13 shown in FIG. 3) of the sound pressure level of the underwater sound wave radiated by the underwater vehicle 1 is the sound wave propagation. The change with distance 6 is shown on a logarithmic scale. Since the underwater acoustic wave diffuses into a spherical surface, the attenuation rate of the underwater acoustic wave is proportional to the square of the distance, as shown in the figure. In FIG. 5, the change in the S / N ratio 17 is relatively expressed with the S / N ratio 17 at the time when the sound wave propagation distance 6 is 30 km as a reference (0 dB).

  FIG. 6 is a diagram for explaining the improvement effect of the estimated azimuth accuracy by integrating the underwater sound wave radiated by the underwater vehicle 1. In FIG. 6, the solid line shows the change of the S / N ratio 17 of the underwater acoustic wave depending on the integration time. That is, the S / N ratio 17 represents the ratio (dB) of the sound pressure level between the sound wave emitted from the underwater vehicle 1 and the natural underwater noise in the input signal to the acoustic sensor 3, and is shown in FIG. This corresponds to the output signal of the S / N ratio calculation unit 13. In FIG. 6, a dotted line shows the change of the direction calculation error of the underwater acoustic wave due to the integration time.

  The underwater sound wave radiated from the underwater vehicle 1 is an artificial mechanical operation sound. When underwater sound waves radiated from the underwater vehicle 1 are integrated for M seconds (M times sampling) with a 1 second period, the sound pressure level is multiplied by the number of integration times, that is, M times. On the other hand, underwater noise, which is 1 / f fluctuation noise in the natural world, has a characteristic of pink noise in which the sound pressure level becomes a square root multiple of M when M seconds are integrated (sampling M times) at a cycle of 1 second. Therefore, as shown in FIG. 6, the longer the integration time (the greater the number of sampling times), the better the S / N ratio 17, and the azimuth calculation error 18 due to underwater noise is reduced.

  Here, the S / N ratio 17 is represented by the following equation, where the integration time of the input signal is M seconds (sampling M times with a 1 second period).

  S / N = M ÷ SQRT (M)

  The azimuth calculation error 18 is expressed as the following equation as a function of integration time.

  Azimuth calculation error = ATAN (SQRT (M) ÷ M) Equation (1)

  Next, the relationship between the integration time (integration period) of the input signal and the azimuth calculation accuracy will be described with reference to FIGS. FIG. 7 shows the time change of the direction calculation error when the integration time is set to 128 seconds. FIG. 8 shows the time change of the direction calculation error when the integration process is not performed. 7 and 8, the solid line indicates the sound wave arrival direction (true value) 7 (see FIG. 1) determined by the speed and elapsed time of the underwater vehicle 1, and the region between the two dotted lines is the above-described equation (1). An azimuth calculation error range 19 calculated based on When the sound wave arrival direction 7 is 90 deg, the underwater vehicle 1 is traveling at the speed of 30 km / h at the position of the closest distance 5 shown in FIG.

  First, the case where the integration time is set relatively long will be described with reference to FIG. Note that FIG. 7 shows the time from the point of 30 minutes in FIG. As the sonic wave arrival direction (true value) 7 approaches 90 deg, the S / N ratio increases as the sound wave propagation distance 6 (see FIG. 1) decreases, and the azimuth calculation error range due to underwater noise The width of 19 becomes narrower. However, due to the influence of the long integration time (128 seconds), the azimuth calculation result is output with a delay of half the integration time. For this reason, in the vicinity of the position of the closest approach distance 5 (90 deg, 1200 seconds), the direction calculation error is rather large. An azimuth error at the time of closest approach is about 26 deg.

  Next, a case where the integration process is not executed (or a case where the integration time is relatively short) will be described with reference to FIG. As the sonic wave arrival direction (true value) 7 approaches 90 deg, the S / N ratio increases as the sound wave propagation distance 6 (see FIG. 1) decreases, and the azimuth calculation error range due to underwater noise The width of 20 becomes narrower. Since the integration process is not executed, there is no delay in the azimuth calculation caused by the integration process as shown in FIG. 7, and the azimuth error at the time of closest approach is about 5 degrees.

  From the above, in the vicinity of the closest approach, the output delay of the processing result due to the long-time integration processing appears remarkably and increases the azimuth error. Therefore, the direction calculation error is smaller when the integration processing is not executed. Recognize. Therefore, it is considered that there is an optimum range of integration time that changes according to the sound wave propagation distance 6 or the sound wave arrival direction 7 and eventually according to the S / N ratio 17.

  Therefore, a case where the integration time is selected according to the S / N ratio of the input signal as in this embodiment will be described.

  FIG. 9 shows an azimuth calculation error corresponding to the case where the integration time is changed according to the result of the S / N ratio calculation of the input signal according to the present embodiment. Here, the integration time is set so that the direction calculation error is about 5 deg.

  In FIG. 9, the solid line indicates the sound wave arrival direction (true value) 7 (see FIG. 1) determined by the speed of the underwater vehicle 1 and the elapsed time. In FIG. 9, a region between two dotted lines indicates an azimuth calculation error range 21 calculated using the above-described equation (1) and the algorithm shown in FIG. 4 according to the present embodiment.

  As shown in FIGS. 7 and 8, it can be seen that in FIG. 9, the azimuth calculation error is smaller over the entire range of time than when the integration time is fixed or fixed to zero.

  According to the first embodiment described above, the integration time is automatically selected in response to the change in the S / N ratio due to the change in the relative distance between the underwater vehicle and the acoustic sensor. The generated output delay is suppressed, and the direction calculation accuracy is improved.

  In the first embodiment, when calculating the arrival direction of the sound wave emitted from the underwater vehicle by sonar, the S / N ratio is utilized by utilizing the characteristic that the underwater noise level attenuates in proportion to the square root of the integration time. An algorithm for calculating the value of is provided.

Second Embodiment
A second embodiment will be described. FIG. 10 is a diagram for explaining an outline of another system for calculating the direction of the underwater vehicle using the towed acoustic sensor.

  In contrast to FIG. 1 and FIG. 10, in the second embodiment, the difference between the system of FIG. 10 and the system of FIG. 1 will be mainly described, and the common points of both systems relate to the system of FIG. 1 described above. Refer to the description.

  In the system shown in FIG. 10, a towed acoustic sensor 23 towed by the ship 22 is used. Corresponding to the time change of the relative distance between the underwater vehicle 1 and the towing acoustic sensor 23, the sound wave propagation distance 6 changes with time. As the sound wave propagation distance 6 changes with time, the S / N ratio of sound waves received by the towed acoustic sensor 23 changes with time. Therefore, the system of FIG. 10 can be expected to improve the azimuth calculation accuracy as in the system of FIG.

  It should be noted that the disclosures of the above patent documents are incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various combinations or selections of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. . That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

Although not particularly limited, the embodiment, the modification, and the like are appended as follows.
(Appendix 1)
In the device that detects the position of the underwater vehicle, the integration processing to improve the S / N ratio conversely causes a processing delay due to the integration time and suppresses an increase in azimuth calculation error. A device that improves the azimuth calculation accuracy by calculating the S / N ratio of the processed signal and performing an appropriate integration process according to the S / N ratio.
(Appendix 2)
The S / N ratio is calculated based on the improvement rate of the S / N ratio by the integration processing of the integration processing unit of the acoustic signal.
(Appendix 3)
The integration processing unit for the acoustic signal is configured to execute in advance a plurality of integration processes with different integration times, and the integration time selection unit for the acoustic signal is optimal from the results of the plurality of integration processes executed in advance. The acoustic signal integrated with the integration time is selected.

DESCRIPTION OF SYMBOLS 1 Underwater vehicle 2 Passing course of underwater vehicle 3 Acoustic sensor 4 Closest position between underwater vehicle and acoustic sensor 5 Closest distance between underwater vehicle and acoustic sensor 6 Sound wave propagation distance 7 Sound arrival direction 8 Sound Sensor Y-axis directivity 9 Acoustic sensor X-axis directivity 10 LPF (low-pass filter)
11 A / D conversion unit 12 FFT processing unit 13 S / N ratio calculation unit (S / N ratio calculation processing unit)
14 Integration processing unit 15 Integration time selection unit (Integration time selection processing unit)
16 Azimuth calculation unit (azimuth calculation processing unit)
17 S / N ratio 18 Direction calculation error 19 Direction calculation error range 20 Direction calculation error range 21 Direction calculation error range 22 Ship 23 Towing acoustic sensor 1101 Sonar device 1102 S / N ratio calculation unit 1103 Integration processing unit 1104 Integration time selection unit 1105 Direction calculation part

Claims (10)

At least one S / N ratio calculator configured to calculate an S / N ratio of an acoustic signal received by the acoustic sensor;
At least one integration processing unit configured to integrate the acoustic signal with a set integration time;
At least one integration time selector configured to select the integration time based on the S / N ratio;
At least one orientation calculator configured to calculate an orientation of the received acoustic signal based on the at least one acoustic signal integrated with the selected integration time;
A sonar device characterized by comprising:   The sonar device according to claim 1, wherein the at least one integration time selection unit is configured to select the integration time of the acoustic signal that has already been integrated.   The at least one S / N ratio calculation unit is different in at least one of presence / absence of the integration processing for the acoustic signal, the integration time for the acoustic signal, a sampling period for the acoustic signal, and a sampling count for the acoustic signal. 3. The sonar device according to claim 1, wherein the sonar device is configured to calculate the S / N ratio based on a plurality of acoustic signals.   The at least one S / N ratio calculation unit is configured to calculate the S / N ratio based on the acoustic signal not subjected to integration processing and the acoustic signal subjected to integration processing. The sonar device according to any one of claims 1 to 3.   The at least one S / N ratio calculation unit causes the integration time selection unit to select a relatively short integration time when the S / N ratio is relatively high, and the S / N ratio is relatively high. The sonar device according to any one of claims 1 to 4, wherein the sonar device is configured to cause the at least one integration time selection unit to select a relatively long integration time when low.   The at least one integration time selection unit sets the integration time relatively long when the detection target is located far from the acoustic sensor, and when the detection target is located near the acoustic sensor. The sonar device according to any one of claims 1 to 5, wherein the sonar device is configured to set the integration time relatively short. The sonar device according to any one of claims 1 to 6, and the acoustic sensor,
The acoustic signal processing system, wherein the acoustic sensor is mounted on a ship or towed by a ship. Calculating the S / N ratio of the acoustic signal received by the acoustic sensor;
The acoustic signal is integrated with a set integration time,
Selecting the integration time based on the S / N ratio;
An acoustic signal processing method, comprising: calculating an azimuth of the received acoustic signal based on at least one of the acoustic signals integrated with the selected integration time. A function of calculating an S / N ratio of an acoustic signal received by the acoustic sensor;
A function of integrating the acoustic signal with a set integration time;
A function of selecting the integration time based on the S / N ratio;
A function of calculating an orientation of the received acoustic signal based on at least one of the acoustic signals integrated with the selected integration time;
An acoustic signal processing program for causing a computer to execute.   A computer is configured to execute a function of calculating an S / N ratio based on a plurality of acoustic signals received by an acoustic sensor and having at least one of integration processing presence / absence, integration time, sampling period, and number of samplings. An acoustic signal processing program.

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