Estimating seafloor compressional sound speed using a long towed horizontal line array

Depth discrimination is a key procedure in acoustic detection or target classification for low-frequency underwater sources. Conventional depth-discrimination methods use a vertical line array, which has disadvantage of poor mobility due to the size of the sensor array. In this paper, we propose a depth-discrimination method for low-frequency sources using a horizontal line array (HLA) of acoustic vector sensors based on mode extraction. First, we establish linear equations related to the modal amplitudes based on modal beamforming in the vector mode space. Second, we solve the linear equations by introducing the total least square algorithm and estimate modal amplitudes. Third, we select the power percentage of the low-order modes as the decision metric and construct testing hypotheses based on the modal amplitude estimation. Compared with a scalar sensor, a vector sensor improves the depth discrimination, because the mode weights are more appropriate for doing so. The presented linear equations and the solution algorithm allow the method to maintain good performance even using a relatively short HLA. The constructed testing hypotheses are highly robust against mismatched environments. Note that the method is not appropriate for the winter typical sound speed waveguide, because the characteristics of the modes differ from those in downward-refracting sound speed waveguide. Robustness analysis and simulation results validate the effectiveness of the proposed method.

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MATCHED FIELD SOURCE LOCALIZATION WITH A HORIZONTAL LINE ARRAY

Journal of Computational Acoustics ◽

10.1142/s0218396x94000208 ◽

1994 ◽

Vol 02 (03) ◽

pp. 315-325

Author(s):

N. R. CHAPMAN ◽

M. L. YEREMY

Keyword(s):

Source Localization ◽

Sound Speed ◽

Water Environment ◽

Horizontal Line ◽

Speed Profile ◽

Field Source ◽

Sound Speed Profile ◽

Line Array ◽

Localization Performance ◽

Experimental Geometry

Matched field source localization performance is investigated for a source in aft endfire of a horizontal line array operating in a deep water environment. Simulations are used to investigate the performance for ideal conditions and in the presence of noise. In particular, the effects of uncertainty in experimental geometry and mismatch in sound speed profile are considered. It is shown that the performance is sensitive to the vertical tilt of the array for relatively small tilt angles of less than 5º. However, the horizontal array is robust to mismatch in the gradient of the sound speed profile at the bottom of the water column. The results of the simulations are interpreted in terms of the characteristics of acoustic propagation in the environment.

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Inversion for Sound Speed Profile by Using a Bottom Mounted Horizontal Line Array in Shallow Water

Chinese Physics Letters ◽

10.1088/0256-307x/27/8/084303 ◽

2010 ◽

Vol 27 (8) ◽

pp. 084303

Author(s):

Li Feng-Hua ◽

Zhang Ren-He

Keyword(s):

Shallow Water ◽

Sound Speed ◽

Horizontal Line ◽

Speed Profile ◽

Sound Speed Profile ◽

Line Array

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Motion compensation for adaptive horizontal line array processing

The Journal of the Acoustical Society of America ◽

10.1121/1.1528929 ◽

2003 ◽

Vol 113 (1) ◽

pp. 245-260 ◽

Cited By ~ 9

Author(s):

T. C. Yang

Keyword(s):

Motion Compensation ◽

Array Processing ◽

Horizontal Line ◽

Line Array

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Reliable Acoustic Path and Direct-Arrival Zone Spatial Gain Analysis for a Vertical Line Array

Sensors ◽

10.3390/s18103462 ◽

2018 ◽

Vol 18 (10) ◽

pp. 3462 ◽

Cited By ~ 1

Author(s):

Chunyu Qiu ◽

Shuqing Ma ◽

Yu Chen ◽

Zhou Meng ◽

Jianfei Wang

Keyword(s):

Sound Propagation ◽

Correlation Coefficients ◽

Deep Ocean ◽

Vertical Line ◽

Horizontal Line ◽

Acoustic Path ◽

Vertical Arrays ◽

Peak Structure ◽

Line Array ◽

Propagation Properties

A method is developed in this paper to calculate the spatial gain of a vertical line array when the plane-wave assumption is not applicable and when the oceanic ambient noise is correlated. The proposed optimal array gain (OAG), which can evaluate the array’s performance and effectively guide its deployment, can be given by an equation in which the noise gain (NG) is subtracted from the signal gain (SG); hence, a high SG and a negative NG can enhance the performance of the array. OAGs and SGs with different array locations are simulated and analyzed based on the sound propagation properties of the direct-arrival zone (DAZ) and the reliable acoustic path (RAP) using ray theory. SG and NG are related to the correlation coefficients of the signals and noise, respectively, and the vertical correlation is determined by the structures of the multipath arrivals. The SG in the DAZ is always high because there is little difference between the multipath waves, while the SG in the RAP changes with the source-receiver range because of the variety of structure in the multiple arrivals. The SG under different conditions is simulated in this work. The “dual peak” structure can often be observed in the vertical directionality pattern of the noise because of the presence of bottom reflection and deep sound channel. When the directions of the signal and noise are close, the conventional beamformer will enhance the correlation of not only the signals but also the noise; thus, the directivity of the signals and noise are analyzed. Under the condition of having a typical sound speed profile, the OAG in some areas of the DAZ and RAP can achieve high values and even exceed the ideal gain of horizontal line array 10 logN dB, while, in some other areas, it will be lowered because of the influence of the NG. The proposed method of gain analysis can provide analysis methods for vertical arrays in the deep ocean under many conditions with references. The theory and simulation are tested by experimental data.

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Batch Processing through Particle Swarm Optimization for Target Motion Analysis with Bottom Bounce Underwater Acoustic Signals

Sensors ◽

10.3390/s20041234 ◽

2020 ◽

Vol 20 (4) ◽

pp. 1234

Author(s):

Raegeun Oh ◽

Taek Lyul Song ◽

Jee Woong Choi

Keyword(s):

Particle Swarm Optimization ◽

Motion Analysis ◽

Acoustic Signals ◽

Batch Processing ◽

Target Motion ◽

Horizontal Line ◽

Swarm Optimization ◽

Conical Angle ◽

Line Array ◽

Target Motion Analysis

A target angular information in 3-dimensional space consists of an elevation angle and azimuth angle. Acoustic signals propagating along multiple paths in underwater environments usually have different elevation angles. Target motion analysis (TMA) uses the underwater acoustic signals received by a passive horizontal line array to track an underwater target. The target angle measured by the horizontal line array is, in fact, a conical angle that indicates the direction of the signal arriving at the line array sonar system. Accordingly, bottom bounce paths produce inaccurate target locations if they are interpreted as azimuth angles in the horizontal plane, as is commonly assumed in existing TMA technologies. Therefore, it is necessary to consider the effect of the conical angle on bearings-only TMA (BO-TMA). In this paper, a target conical angle causing angular ambiguity will be simulated using a ray tracing method in an underwater environment. A BO-TMA method using particle swarm optimization (PSO) is proposed for batch processing to solve the angular ambiguity problem.

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