Sound wave propagation model selection method, sound wave propagation model selection device, and propagation loss calculation system

Abstract

To provide a sound wave propagation model selection method, a sound wave propagation model selection device and a propagation loss calculation system that automatically select whether to use a sound ray model or a wave model for each calculation condition in sonar detection performance prediction, while balancing calculation time and accuracy.SOLUTION: In the sound wave propagation model selection method for selecting whether to use a sound ray model or a wave model as a sound wave propagation model used for sonar detection performance prediction for each of multiple calculation conditions used for sonar detection performance prediction, calculation time using the sound ray model is predicted for each of multiple calculation conditions, calculation time using the wave model is predicted for each of the multiple calculation conditions, and a sound wave propagation model with shorter predicted calculation time between the sound ray model and the wave model is selected for each of multiple calculation conditions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sound wave propagation model selection method, a sound wave propagation model selection device, and a propagation loss calculation system used for predicting the detection performance of a sonar. [Background technology]

[0002] It is known that sonar detection performance predictions are performed to effectively operate sonars when detecting the presence of targets. Sonar detection performance predictions aim to support effective sonar operation and require calculations for multiple calculation conditions. For example, by predicting detection performance for many frequencies of sound waves emitted from a target, it is possible to determine which frequencies are effective for waiting for the target. Furthermore, sonar detection performance also changes because sound propagation characteristics vary with depth characteristics of sound speed (hereinafter referred to as sound speed profile) and water depth. Therefore, by predicting detection performance for various sound speed profiles and water depths at many locations, it is possible to determine which locations are effective for waiting for the target.

[0003] One of the elements necessary for predicting detection performance is the propagation loss from the target to the sonar, calculated using a sound wave propagation model. As disclosed in Non-Patent Document 1, representative sound wave propagation models include the sound ray model (see pages 155-175 of Non-Patent Document 1) and the wave model (see pages 65-73 of Non-Patent Document 1), each with its own characteristics. The sound ray model is a sound wave propagation model that simplifies calculations using high-frequency approximation, and accuracy decreases at low frequencies, resulting in larger errors in propagation loss. The amount of calculation required for the sound ray model varies little with frequency, but tends to increase as the water depth becomes shallower. This is because the shallower the water depth, the more times a sound wave emitted from the target at the same depression angle is reflected between the sea surface and the seabed, increasing the number of sound ray paths that reach the sonar and affect the propagation loss. As described above, the sound ray model is characterized by the fact that the shallower the water depth, the greater the amount of calculation required, resulting in longer calculation times.

[0004] On the other hand, as a wave model, for example, the parabolic equation method (hereinafter referred to as the PE method) is known (see pages 457 to 471 of Non-Patent Document 1). The PE method is a sound wave propagation model that discretizes and numerically calculates the wave equation. In the wave model, when the wave equation in the wave model is discretized and solved, the underwater space is gridded at intervals corresponding to the wavelength of the sound wave emitted from the target. Therefore, accuracy does not decrease even at low frequencies, and accuracy is higher than that of the acoustic ray model across the entire frequency band. However, in the wave model, the number of grids in the depth direction of the space increases at high frequencies or in deep sea areas, increasing the amount of calculation. As described above, the wave model is more accurate than the acoustic ray model across the entire frequency band, but the higher the frequency and the shorter the wavelength, and the deeper the water depth, the greater the amount of calculation and the longer the calculation time. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Finn B. Jensen, William A. Kuperman, Michael B. Porter, Henrik Schmidt Jensen, “Computational Ocean Acoustics Second edition”, Springer, 2011, p.65-73,155-175,457-471 Summary of the Invention [Problem to be solved by the invention]

[0006] For users predicting sonar detection performance, it was a burden to choose whether to use the ray model or the wave model for each calculation condition while balancing calculation time and accuracy.

[0007] The present invention has been made in light of the above-mentioned problems, and aims to provide a sound wave propagation model selection method, a sound wave propagation model selection device, and a propagation loss calculation system that automatically select whether to use a sound ray model or a wave model for each calculation condition in predicting sonar detection performance, while balancing calculation time and accuracy. [Means for solving the problem]

[0008] The sound wave propagation model selection method according to the present invention is a method for selecting either a sound ray model or a wave model as a sound wave propagation model to be used for predicting sonar detection performance for each of a plurality of calculation conditions used for predicting sonar detection performance, and predicts the calculation time using the sound ray model for each of the plurality of calculation conditions, predicts the calculation time using the wave model for each of the plurality of calculation conditions, and selects the sound wave propagation model with the shortest predicted calculation time from the sound ray model and the wave model for each of the plurality of calculation conditions. When an allowable time is set that indicates the time allowed as the total calculation time using the selected sound wave propagation model under all calculation conditions, after selecting a sound wave propagation model for each of the multiple calculation conditions, the sound wave propagation model used under the calculation conditions in which the sound ray model is selected is replaced with the wave model within the allowable time in order from the calculation condition with the smallest difference between the calculation time using the wave model and the calculation time using the sound ray model. .

[0009] The sound wave propagation model selection device and propagation loss calculation system of the present invention utilize the above method. [Effects of the Invention]

[0010] In the sound wave propagation model selection method, sound wave propagation model selection device, and propagation loss calculation system of the present invention, a wave model which requires short calculation times and is highly accurate is selected for low frequencies and shallow water areas, and a sound ray model which requires less calculation time is selected for other calculation conditions. Therefore, the sound wave propagation model selection method, sound wave propagation model selection device, and propagation loss calculation system of the present invention can automatically select whether to use a sound ray model or a wave model for each calculation condition in predicting sonar detection performance, while balancing calculation time and accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a functional block diagram showing a propagation loss calculation system according to a first embodiment. [Figure 2] 4 is a numerical table used to predict the calculation time in the acoustic ray model according to the first embodiment. [Figure 3] 4 is a flowchart showing a sound wave propagation model selection method according to the first embodiment. [Figure 4] FIG. 10 is a functional block diagram showing a propagation loss calculation system according to a second embodiment. [Figure 5] 10 is a flowchart showing a sound wave propagation model selection method according to the second embodiment. [Figure 6] FIG. 11 is a functional block diagram showing a propagation loss calculation system according to a third embodiment. [Figure 7] 11 is a diagram for explaining sound channels and sound rays trapped in the sound channels according to the third embodiment. FIG. [Figure 8] 11 is a flowchart showing a sound wave propagation model selection method according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 FIG. 1 is a functional block diagram showing a propagation loss calculation system 100 according to a first embodiment. The propagation loss calculation system 100 calculates the propagation loss from a target to a sonar based on a sound wave propagation model. The propagation loss from a target to a sonar is one of the elements required for predicting the detection performance of a sonar. Hereinafter, the propagation loss from a target to a sonar may be simply referred to as the propagation loss. As shown in FIG. 1, the propagation loss calculation system 100 includes an input device 10, a sound wave propagation model selection device 20, a propagation loss calculation device 30, and a storage device 40.

[0013] The input device 10 is used to input input data consisting of N calculation conditions, which is data for calculating propagation loss. The input data is transmitted to the sound wave propagation model selection device 20 and the propagation loss calculation device 30. The input device 10 is, for example, a keyboard or a touch panel. Each calculation condition is assigned a calculation condition number, where n=1, 2, ..., N. The calculation elements included in each of the N calculation conditions are the wavelength λ of the sound wave radiated from the target, n , water depth H n , calculated maximum distance R n , sound speed profile (Z nk ,C nk )(k=1,2,…,K n ), target depth ZT n , and sonar depth ZS n The sound speed profile is nk and the speed of sound C at that depth nk and K n is the depth Z for each calculation condition number n=1,2,...,N nk and the speed of sound C nk The calculation conditions are different from each other in any or all of the calculation elements included in the calculation conditions.

[0014] The sound wave propagation model selection device 20 selects whether to use an acoustic ray model or a wave model as the sound wave propagation model for calculating propagation loss, based on the calculation conditions input from the input device 10. Information indicating the selected sound wave propagation model is transmitted to the propagation loss calculation device 30.

[0015] The sound propagation model selection device 20 is configured with dedicated hardware, or a CPU (also referred to as a central processing unit, processing device, arithmetic unit, microprocessor, or processor) that executes programs stored in the storage device 40. Each functional unit realized by the sound propagation model selection device 20 may be realized by separate hardware, or each functional unit may be realized by a single piece of hardware. Each function executed by the sound propagation model selection device 20 is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the storage device 40. The CPU realizes each function by reading and executing the programs stored in the storage device 40.

[0016] The sound wave propagation model selection device 20 has, as functional units, an acoustic ray model prediction unit 21, a wave model prediction unit 22, and a selection unit 23. The acoustic ray model prediction unit 21 selects the water depth H n and calculate the maximum distance R n From the calculation time Tray n Specifically, the sound ray model prediction unit 21 predicts the calculation time Tray n Calculate.

[0017] First, the calculation time for the sound ray model is n is the water depth H n The shallower the distance, the longer the distance. n The calculation time is directly proportional to the water depth h m (m=1,2,…,M) and a certain maximum distance R (0) Calculation time tm (m=1,2,…,M) and the relationship (h m ,t m ) (m=1, 2, . . . , M) are stored in the storage device 40 as a numerical table as shown in FIG. 2. FIG. 2 shows the calculation time Tray n The acoustic ray model prediction unit 21 then calculates the water depth H n and calculate the maximum distance R n Therefore, the calculation time Tray using the sound ray model is calculated by the following equation (1). n Calculate.

[0018]

number

[0019] Here, m' is the number of h m '-1≦H n <h m ' is satisfied. Equation (1) is the calculated maximum distance R (0) The calculation time for m ,t m ) (m=1,2,…,M) by linear interpolation, and the calculation time is calculated as the maximum distance R n Calculation time for Tray n This is the formula that converts to:

[0020] The wave model prediction unit 22 calculates the water depth H for each of the input calculation condition numbers n=1, 2, ..., N. n , calculated maximum distance R n and wavelength λ n From the calculation time Twave by the wave model n Specifically, the wave model prediction unit 22 predicts the calculation time Tray by the following method. n Calculate.

[0021] Here, we consider the PE method, which is widely used as a wave model to predict the detection performance of sonars. The PE method is a sound wave propagation model that discretizes the wave equation and calculates it numerically. Since calculations are performed by dividing the water into depth and distance grids at intervals proportional to the wavelength, the calculation time is proportional to the number of grids. Therefore, for a certain water depth H (0) , calculated maximum distance R (0) (The maximum calculated distance R (0) ), and wavelength λ (0) Calculation time T (0) is measured in advance and stored in the storage device 40. The wave model prediction unit 22 uses the input water depth H n , calculated maximum distance R n and wavelength λ n From the following equation (2), the calculation time Twave by the wave model is n Calculate.

[0022]

number

[0023] Equation (2) is the water depth H (0) , calculated maximum distance R (0) and wavelength λ (0) The number of grid points for depth and distance and the water depth H n , calculated maximum distance R n and wavelength λ n The calculation time, which was measured in advance, was corrected by the ratio of the depth and distance grid number to the calculation time Twave. n This is the formula for calculating

[0024] The selection unit 23 selects the calculation time Tray using the sound ray model for each of the calculation condition numbers n=1, 2, . . . , N. n and the calculation time Twave based on the wave model n and to select the sound propagation model, and the result is stored in the model flag F n where the model flag F n is F n =0 is the wave model, F n= 1 means a sound ray model. Specifically, the selection unit 23 selects the model flag F n Set.

[0025] The selection unit 23 selects the calculation time Tray using the sound ray model for each of the calculation condition numbers n=1, 2, . . . , N. n and the calculation time Twave based on the wave model n From Model Flag F n is set by equation (3).

[0026]

number

[0027] Equation (3) is the calculation time Twave by the wave model for each calculation condition number n=1, 2, ..., N. n The calculation time using the acoustic ray model is n In the following cases, the wave model is selected as the sound propagation model. Otherwise, the calculation time for the wave model is Twave. n The calculation time using the acoustic ray model is n This means that the ray model is selected when the

[0028] The propagation loss calculation device 30 calculates the model flag F n Using the acoustic wave propagation model set in, the water depth H for each calculation condition number n=1,2,…,N is calculated. n , calculated maximum distance R n , wavelength λ n , sound speed profile (Z nk ,C nk )(k=1,2,…,K n ), target depth ZT n and sonar depth ZS n from a predetermined distance r j Path loss TL for (j=1,2,…,J) n (r j ) (j=1, 2, ..., J, n=1, 2, ..., N). The propagation loss calculation device 30 calculates the model flag F nIf is 0, the model flag F n If is 1, the propagation loss TL n (r j ) (j=1,2,...,J, n=1,2,...N).

[0029] The storage device 40 stores data of several water depths h used in the acoustic ray model prediction unit 21. m and a certain calculated maximum distance R (0) Calculation time t m The relationship (h m ,t m ) (m=1, 2, ..., M) is stored in the storage device 40. The storage device 40 also stores a numerical table indicating a water depth H (0) , calculated maximum distance R (0) , and wavelength λ (0) Calculation time T (0) In addition, the storage device 40 stores the processing results of the sound wave propagation model selection device 20 and the propagation loss calculation device 30. The storage device 40 is, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM.

[0030] 3 is a flowchart showing a sound wave propagation model selection method according to the first embodiment. The sound wave propagation model selection method executed by the sound wave propagation model selection device 20 will be described with reference to FIG. 3. First, the sound ray model prediction unit 21 calculates the water depth H n and calculate the maximum distance R n Therefore, the calculation time using the sound ray model is n Next, the wave model prediction unit 22 calculates the input water depth H n , calculated maximum distance R n and wavelength λ n From the calculation time Twave by the wave model n (Step S2). Then, the selection unit 23 calculates the calculation time Tray n and the calculation time Twave based on the wave model n Compared with the model flag F n(Step S3) The order of steps S1 and S2 may be reversed as appropriate.

[0031] As shown in equation (2), the longer the wavelength and the lower the frequency, the longer the calculation time Twave of the wave model. n On the other hand, the calculation time for the sound ray model is n Furthermore, the shallower the water depth, the longer the calculation time Twave of the wave model. n is shortened, whereas the calculation time for the sound ray model is n Therefore, the wavelength λ n is long and the frequency is low, and the water depth is H n Under shallow calculation conditions, the calculation time for the wave model is Twave n may be shorter, in which case a wave model is selected. That is, in the sound wave propagation model selection method, sound wave propagation model selection device 20, and propagation loss calculation system 100 of the first embodiment, a wave model with short calculation time and high accuracy is selected for low frequencies and shallow waters, and a sound ray model with short calculation time is selected for other calculation conditions. Therefore, according to the sound wave propagation model selection method, sound wave propagation model selection device 20, and propagation loss calculation system 100 of the first embodiment, it is possible to automatically select whether to use a sound ray model or a wave model for each calculation condition in predicting sonar detection performance, while balancing calculation time and accuracy. This also reduces the burden on the user who predicts sonar detection performance.

[0032] Furthermore, according to the propagation loss calculation system 100 of the first embodiment, for each of a plurality of calculation conditions, a propagation model that predicts a shorter calculation time is selected and the propagation loss TL n (r j ) (j=1,2,...,J,n=1,2,...,N), it is possible to predict detection performance with minimal calculation time.

[0033] Embodiment 2 4 is a functional block diagram showing a propagation loss calculation system 100A according to the second embodiment. As shown in FIG. 4, the second embodiment calculates a propagation loss by adding an allowable time T max In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted, and the description will focus on the differences from the first embodiment.

[0034] The acoustic ray model prediction unit 21 and the wave model prediction unit 22 of the propagation model selection device, and the propagation loss calculation device 30 have the same configuration as in the first embodiment.

[0035] The selection unit 23A selects the calculation time Tray of the sound ray model for each of the calculation condition numbers n=1, 2, . . . , N. n and the calculation time of the wave model, Twave n In addition, the allowable time T max to select the sound propagation model and set the result as the model flag F n where the allowable time T max is the time allowed as the total calculation time, which indicates the total calculation time for the sound wave propagation models selected under all N calculation conditions, and is set by the user as input data via the input device 10. n The definitions are the same as in the first embodiment.

[0036] A specific operation of the selection unit 23A will be described. First, the selection unit 23A selects the calculation time Tray in the acoustic ray model in the same manner as the selection unit 23 in the first embodiment. n and the calculation time Twave in the wave model n Based on the magnitude relationship with n In this case, the total calculation time is T min is calculated using the following formula (4).

[0037]

number

[0038] Here, the calculation time T for each calculation condition number n=1, 2, ..., N n is expressed by the following equation (5), and corresponds to the calculation time when the sound wave propagation model selected by the selection unit 23 in the first embodiment is used.

[0039]

number

[0040] Next, the selection unit 23A selects the total calculation time T min and the allowable time T max Compare with T min ≧T max In this case, the allowable time T max , the selection unit 23A stops the process here and selects the set F n In this case, the result is the same as the result output by the selection unit 23 in the first embodiment. min <T max In this case, the allowable time T max Therefore, the selection unit 23A selects some of the calculation conditions for which the acoustic ray model is selected within the allowable time T max Change to a wave model within the range that satisfies the above.

[0041] Specifically, the selection unit 23A changes from the acoustic ray model to the wave model in the following manner. First, the selection unit 23A selects the predicted acoustic ray model's calculation time Tray n and the calculation time of the wave model, Twave n The difference (hereinafter referred to as the calculation time difference) ΔT n is calculated using the following formula (6).

[0042]

number

[0043] In equation (6), F n When = 0, ΔT n =∞ in order to substantially exclude from the following processing the calculation conditions for which the wave model has already been selected.

[0044] The selection unit 23A selects the calculation time difference ΔT n After calculating (n=1, 2, ..., N), the results are sorted in ascending order. Here, the sorted sequence is shown in equation (7), and for each ν in equation (7), the index number before sorting is iν In other words, equation (8) holds true for the calculation time difference.

[0045]

number

[0046]

number

[0047] Next, the selection unit 23A calculates the equation (9) while increasing the value of N' by 1 in order from N'=1, and N’ >T max -T min When this happens, stop increasing N'.

[0048]

number

[0049] For ν=1, 2, ..., N'-1, the calculation time difference shown in equation (8) satisfies the relationship shown in the following equation (10) based on equation (6). The model flag F corresponding to the range of ν=1, 2, ..., N'-1 iν The selection unit 23A selects the model flag F corresponding to the range of ν=1, 2, ..., N'-1. iν is replaced with 0, that is, with the wave model. As a result, among the calculation conditions in which the sound ray model was selected in order to prioritize calculation time in the first embodiment, the sound wave propagation model for some calculation conditions in which the increase in calculation time is small compared to the sound ray model is replaced with the sound wave propagation model for the allowable time T max It can be replaced by a wave model within the range.

[0050]

number

[0051] Then, the selection unit 23A selects the finally obtained model flag F n Output (n=1,2,…,N).

[0052] Fig. 5 is a flowchart showing a sound wave propagation model selection method according to the second embodiment. The sound wave propagation model selection method executed by the sound wave propagation model selection device 20 will be described using Fig. 5. Steps S1 to S3 are the same as those in the first embodiment, and therefore their description will be omitted. In the sound wave propagation model selection method according to the second embodiment, after the processing of step S3, a calculation time difference ΔT between the calculation time based on the sound ray model and the calculation time based on the wave model is calculated. n Based on the results of sorting in ascending order, the model flag F n (Step S4).

[0053] In the sound wave propagation model selection method, sound wave propagation model selection device 20, and propagation loss calculation system 100A of embodiment 2, as in embodiment 1, a wave model with short calculation time and high accuracy is selected for low frequencies and shallow waters, and a sound ray model with short calculation time is selected for other calculation conditions. Therefore, according to the sound wave propagation model selection method, sound wave propagation model selection device 20, and propagation loss calculation system 100A of embodiment 2, it is possible to automatically select whether to use a sound ray model or a wave model for each calculation condition in sonar detection performance prediction, while balancing calculation time and accuracy. This also reduces the burden on the user who is predicting sonar detection performance.

[0054] Furthermore, according to the second embodiment, among the calculation conditions in which the acoustic ray model was selected with priority given to calculation time in the first embodiment, the acoustic wave propagation model for some calculation conditions in which the increase in calculation time is small compared to the acoustic ray model is selected within the allowable time T maxThe calculation condition under which the increase in calculation time when replacing the acoustic ray model with the wave model is small is wavelength λ n is longer, that is, the frequency is lower, and the water depth H n For such low frequency calculation conditions, the propagation loss TL can be calculated by using a wave model. n (r j ) (j=1,2,...,J, n=1,2,...,N) can be used to improve the accuracy.

[0055] Embodiment 3 Fig. 6 is a functional block diagram showing a propagation loss calculation system 100B according to embodiment 3. As shown in Fig. 6, embodiment 3 differs from embodiment 2 in that it includes a wave index calculation unit 24. In embodiment 3, the same components as those in embodiment 2 are denoted by the same reference numerals and description thereof will be omitted, and the description will focus on the differences from embodiment 2.

[0056] The acoustic ray model prediction unit 21 and the wave model prediction unit 22 of the propagation model selection device, and the propagation loss calculation device 30 have the same configurations as those in the first and second embodiments.

[0057] The wave index calculation unit 24 calculates the wavelength λ n , sound speed profile (Z nk ,C nk )(k=1,2,…,K n ), target depth ZT n and sonar depth ZS n The wave index I is used to show the degree to which calculations using the wave model are better than those using the acoustic ray model in terms of accuracy. n Calculate the Wave Index I n The smaller the value of is, the more accurate the calculation is when it is performed using the wave model rather than the acoustic ray model.

[0058] Specific Wave Indicators I n 7 is a diagram for explaining sound channels and sound rays trapped in the sound channels according to the third embodiment. First, the wave index In This section explains the concept of sound channels. In the ocean, there are sound channels formed by sound speed profiles. As shown in Figure 7, sound channels extend across a range of depths, with the axis at the depth where the sound speed is minimum. There are two possible combinations of upper and lower ends. The first is a combination where the upper end is a depth shallower than the sound channel axis where the sound speed is maximum, and the lower end is a depth deeper than the sound channel axis where the sound speed is equal to the sound speed at the upper end. However, if there is no depth shallower than the sound channel axis where the sound speed is maximum, the upper end is the sea surface. Also, if there is no depth deeper than the sound channel axis where the sound speed is equal to the sound speed at the upper end, the lower end is the seafloor. The second is a combination where the lower end is a depth deeper than the sound channel axis where the sound speed is maximum, and the upper end is a depth shallower than the sound channel axis where the sound speed is equal to the sound speed at the lower end. However, if there is no depth deeper than the sound channel axis where the sound speed is maximum, the lower end is the seafloor. Also, if there is no depth shallower than the sound channel axis where the sound speed is equal to the depth at the bottom, the top will be the sea surface. The example sound channel shown in Figure 7 corresponds to the first combination, with the top end being shallower than the sound channel axis and at a depth where the sound speed is maximum, and the bottom end being deeper than the sound channel axis and at a depth equal to the sound speed at the top.

[0059] A part of the sound waves emitted from a target within the depth range of the sound channel (the width of this depth range will be referred to as the depth width hereinafter) is confined, or trapped, in this sound channel and propagates through the ocean, as shown as sound rays in Figure 7. However, in reality, sound waves may not be completely trapped and may leak out of the sound channel. In such cases, the propagation loss TL calculated by the sound ray model may be n (r j ) (j=1,2,…,J, n=1,2,…,N) accuracy decreases. Sound waves are less likely to be trapped in sound channels in two cases:

[0060] The first is the wavelength of the sound wave, λ n The depth width of the sound channel is determined by the sound velocity profile (Znk ,C nk )(k=1,2,…,K n ), target depth ZT n and sonar depth ZS n is determined by, and hereafter, ΔZ n The sound ray represents the sound wave propagation in the limit where the wavelength is considered to be 0, and in that limit, the depth width of the sound channel is ΔZ n However, when the wavelength becomes longer and the depth-to-wavelength ratio becomes smaller, the sound wave becomes less trapped, and the propagation loss TL calculated by the sound ray model n (r j ) (j=1,2,…,J, n=1,2,…,N) will have lower accuracy.

[0061] The second is when the sound channel width is small. Here, the sound width is the maximum value of the sound speed within the depth range of the sound channel, C max and the minimum sound speed within the depth range of the sound channel, C min , i.e., the difference ΔC between the speed of sound at the target depth and the speed of sound at the sonar depth, whichever is greater. n =C max -C min The sound speed width ΔC n is the depth width ΔZ n Similarly, the sound speed profile (Z nk ,C nk )(k=1,2,…,K n ), target depth ZT n and sonar depth ZS n It is determined by the sound speed width ΔC n When becomes smaller, the radiation angle range of the sound rays trapped in the sound channel becomes narrower. This is because the sound speed at the target depth is (T) This is because, when θ is set, the range of the radiation angle θ of the sound ray trapped in the sound channel is expressed by Snell's law as shown in equation (11).

[0062]

number

[0063] Propagation loss TL based on sound ray model n (r j ) (j=1,2,…,J, n=1,2,…,N) is calculated on the assumption that the radiation angle range of the sound rays trapped in the sound channel is sufficiently wide. However, when the angle range is narrow, the propagation loss TL calculated by the sound ray model becomes n (r j ) (j=1,2,…,J, n=1,2,…,N) will have lower accuracy.

[0064] Based on the above two cases, the wave index I is calculated as shown in equation (12). n is defined.

[0065]

number

[0066] Equation (12) shows the product of the depth width to wavelength ratio and the sound speed width. n The smaller is the propagation loss TL calculated by the sound ray model, n (r j ) (j=1,2,…,J, n=1,2,…,N) accuracy decreases, the propagation loss TL n (r j ) (j=1, 2, . . . , J, n=1, 2, . . . , N) is assumed to result in a greater improvement in the accuracy of the acoustic ray model.

[0067] Above Wave Indicators I n Based on the idea of n is calculated as follows:

[0068] First, the wave index calculation unit 24 calculates the sound speed profile (Z nk ,C nk )(k=1,2,…,K n) of the multiple sound channels included in the target depth ZT n and sonar depth ZS n The wave index calculation unit 24 then selects the sound channel with the smallest depth difference from among those sound channels and calculates the depth difference as ΔZ. n , the sound speed difference is ΔC n Finally, the wave index I n Calculate.

[0069] Returning to FIG. 6, the selection unit 23B selects the calculation time Tray of the sound ray model for each of the calculation condition numbers n=1, 2, . . . , N. n , the calculation time of the wave model, Twave n and the allowable time T max In addition to Wave Indicator I n to select the sound propagation model and set the result as the model flag F n In addition, the model flag F n The definitions are the same as in the first and second embodiments.

[0070] The selection unit 23B has a calculation time difference ΔT with the selection unit 23A of the second embodiment. n (n=1, 2, . . . , N) is rearranged in a different way. n (n=1, 2, ..., N) are sorted in ascending order, but the selection unit 23B sorts the wave index I n (n=1, 2, ..., N) are rearranged in ascending order. Here, the rearranged sequence is shown in equation (13), and for each ν in equation (13), the index number before rearrangement is iν In other words, the wave index I n Regarding this, equation (14) holds.

[0071]

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[0072]

number

[0073] And the calculation time difference ΔT n The sequence (equation (7)) obtained by rearranging (n=1, 2, ..., N) is generated by equation (8). The subsequent processing is the same as in the second embodiment. That is, the selection unit 23B calculates equation (9) while sequentially increasing the value of N' by 1 starting from N'=1, and selects Δτ(N')>T max -T min Then, the selection unit 23B selects the model flag F corresponding to the range of ν=1, 2, ..., N'-1. iν is replaced with 0, that is, the wave model. As a result, among the calculation conditions in which the acoustic ray model was selected in order to prioritize calculation time in the first embodiment, the acoustic wave propagation model for some calculation conditions in which the accuracy is more improved when calculated using the wave model than when calculated using the acoustic ray model is replaced with 0, that is, the wave model. max It can be replaced by a wave model within the range.

[0074] Fig. 8 is a flowchart showing a sound wave propagation model selection method according to the third embodiment. The sound wave propagation model selection method executed by the sound wave propagation model selection device 20 will be described with reference to Fig. 8. Steps S1 to S3 are the same as those in the first embodiment, and therefore their description will be omitted. In the sound wave propagation model selection method according to the third embodiment, after the processing of step S3, a calculation time difference ΔT between the calculation time based on the sound ray model and the calculation time based on the wave model is calculated. n , the wave indicator I n Based on the results of sorting in ascending order, the model flag F n (Step S5).

[0075] In the sound wave propagation model selection method, sound wave propagation model selection device 20, and propagation loss calculation system 100B of embodiment 3, as in embodiment 1, a wave model with short calculation time and high accuracy is selected for low frequencies and shallow waters, and a sound ray model with short calculation time is selected for other calculation conditions. Therefore, according to the sound wave propagation model selection method, sound wave propagation model selection device 20, and propagation loss calculation system 100B of embodiment 3, it is possible to automatically select whether to use a sound ray model or a wave model for each calculation condition in sonar detection performance prediction, while balancing calculation time and accuracy. This also reduces the burden on the user who is predicting sonar detection performance.

[0076] Furthermore, according to the third embodiment, the wave index I n (n=1,2,…,N) in ascending order of allowable time T max The acoustic ray model is replaced with the wave model within the range. This makes it possible to accurately extract calculation conditions that result in a high degree of improvement in accuracy when calculated using the wave model compared to when calculated using the acoustic ray model, and to obtain the overall propagation loss TL for N calculation conditions within the calculation time allowed by the user. n (r j ) (j=1,2,...,J, n=1,2,...,N) can be calculated with higher accuracy.

[0077] The above is a description of the embodiments of the present invention, but the present invention is not limited to the configurations of the above embodiments and various modifications and combinations are possible within the scope of the technical concept. For example, if input data can be transmitted to the sound wave propagation model selection device 20 and the propagation loss calculation device 30 by an external device or the like in which the input data is stored, the input device 10 may be omitted from the propagation loss calculation system. Furthermore, some of the functional units of the sound wave propagation model selection device 20 may be realized by a sonar or other device external to the sound wave propagation model selection device 20. In this case, a sound wave propagation model selection system that executes the sound wave propagation model selection method described in the first to third embodiments is configured by enabling transmission and reception of signals between the sound wave propagation model selection device 20 and the sonar or other device external to the sound wave propagation model selection device 20. [Explanation of symbols]

[0078] 10 Input device, 20 Sound wave propagation model selection device, 21 Sound ray model prediction unit, 22 Wave model prediction unit, 23 Selection unit, 23A Selection unit, 23B Selection unit, 24 Wave index calculation unit, 30 Propagation loss calculation device, 40 Storage device, 100 Propagation loss calculation system, 100A Propagation loss calculation system, 100B Propagation loss calculation system.

Claims

1. A sound wave propagation model selection method for selecting either a sound ray model or a wave model as a sound wave propagation model used to predict the detection performance of a sonar for each of a plurality of calculation conditions used to predict the detection performance of a sonar, predicting a calculation time using the acoustic ray model for each of the plurality of calculation conditions; predicting a calculation time using the wave model for each of the plurality of calculation conditions; selecting the sound wave propagation model having the shortest predicted calculation time from the sound ray model and the wave model for each of the plurality of calculation conditions; When an allowable time indicating an allowable time as the total calculation time by the sound wave propagation model selected under all the calculation conditions is set, After selecting the sound wave propagation model for each of the plurality of calculation conditions, The sound wave propagation model used in the calculation conditions under which the sound ray model is selected is replaced with the wave model within the allowable time in order from the calculation conditions under which the difference between the calculation time using the wave model and the calculation time using the sound ray model is smallest. Sound propagation model selection method.

2. A sound wave propagation model selection method for selecting either a sound ray model or a wave model as a sound wave propagation model to be used in predicting the detection performance of a sonar for each of a plurality of calculation conditions used in predicting the detection performance of a sonar, comprising: predicting a calculation time using the acoustic ray model for each of the plurality of calculation conditions; predicting a calculation time using the wave model for each of the plurality of calculation conditions; selecting the sound wave propagation model having the shortest predicted calculation time from the sound ray model and the wave model for each of the plurality of calculation conditions; When an allowable time indicating an allowable time as the total calculation time by the sound wave propagation model selected under all the calculation conditions is set, After selecting the sound wave propagation model for each of the plurality of calculation conditions, The sound wave propagation model used under the calculation conditions under which the sound ray model is selected is replaced with the wave model within the allowable time in order of the degree of improvement in accuracy when calculated using the wave model compared to when calculated using the sound ray model. Sound propagation model selection method.

3. From the sound speed profile, target depth, and sonar depth constituting each of the plurality of calculation conditions, a depth width, which is the depth difference between the upper end and the lower end of the depth range of the sound channel that includes both the target depth and the sonar depth, and a sound speed width, which is the difference between the maximum and minimum values ​​of the sound speed of the sound channel, are calculated; From the calculated depth width and sound velocity width, and the wavelength of the sound wave emitted from the target, the degree of improvement in accuracy when calculated using the wave model compared to when calculated using the sound ray model is calculated. The sound propagation model selection method according to claim 2 .

4. A sound wave propagation model selection device that selects either a sound ray model or a wave model as a sound wave propagation model used to predict the detection performance of a sonar for each of a plurality of calculation conditions used to predict the detection performance of a sonar, an acoustic ray model prediction unit that predicts a calculation time using the acoustic ray model for each of the plurality of calculation conditions; a wave model prediction unit that predicts a calculation time using the wave model for each of the plurality of calculation conditions; a selection unit that selects, for each of the plurality of calculation conditions, the sound wave propagation model that has the shortest predicted calculation time from the sound ray model and the wave model, When an allowable time indicating an allowable time as the total calculation time by the sound wave propagation models selected under all the calculation conditions is set, the selection unit: After selecting the sound wave propagation model for each of the plurality of calculation conditions, The sound wave propagation model used in the calculation conditions under which the sound ray model is selected is replaced with the wave model within the allowable time in order from the calculation conditions under which the difference between the calculation time using the wave model and the calculation time using the sound ray model is smallest. Sound propagation model selection device.

5. A sound wave propagation model selection device that selects either a sound ray model or a wave model as a sound wave propagation model used in predicting the detection performance of a sonar for each of a plurality of calculation conditions used in predicting the detection performance of a sonar, an acoustic ray model prediction unit that predicts a calculation time using the acoustic ray model for each of the plurality of calculation conditions; a wave model prediction unit that predicts a calculation time using the wave model for each of the plurality of calculation conditions; a selection unit that selects, for each of the plurality of calculation conditions, the sound wave propagation model that has the shortest predicted calculation time from the sound ray model and the wave model, When an allowable time indicating an allowable time as the total calculation time by the sound wave propagation models selected under all the calculation conditions is set, the selection unit: After selecting the sound wave propagation model for each of the plurality of calculation conditions, The sound wave propagation model used under the calculation conditions under which the sound ray model is selected is replaced with the wave model within the allowable time in order of the degree of improvement in accuracy when calculated using the wave model compared to when calculated using the sound ray model. Sound propagation model selection device.

6. The sound wave propagation model selection device according to claim 4 or 5; a propagation loss calculation device that calculates a propagation loss based on the sound wave propagation model selected by the sound wave propagation model selection device and a plurality of the calculation conditions. Propagation loss calculation system.

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