Mode filtering approaches to acoustic source depth discrimination

Premus, V.; Ward, James E.; Richmond, Christ D.

doi:10.1109/acssc.2004.1399387

Cited by 16 publications

(16 citation statements)

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“…The result is a wider mainlobe and higher sidelobes in wave number, which degrades depth discrimination performance of partially spanning VLAs. 12 As an HLA is generally confined to a single depth, or at most a few meters in depth if it is towed with some nominal amount of cant, it possesses no capacity to resolve modes based on the natural orthogonality of the depth-dependent mode functions. In order to resolve any modal structure, the HLA must rely on the projection of its horizontal aperture along the source azimuth to recognize differences in spatial phase periodicity between modes of different horizontal wave numbers.…”

Section: Mode Filtering With a Horizontal Line Arraymentioning

confidence: 99%

“…1 We begin the discussion in the context of a vertical line array (VLA), an aperture more naturally suited to the resolution of depthdependent spatial structure in the received acoustic field. The Helmholtz wave equation, which describes the spatial dependence of the received pressure field, p, in a medium characterized by the speed of propagation, cðzÞ, and density, qðzÞ, is given by 5 1 r @ @r r @p @r þ qðzÞ @ @z 1 qðzÞ…”

Section: Phenomenology: the Physics Of Mode Trappingmentioning

confidence: 99%

“…The basic concept, first introduced in Ref. 1, is general and applicable to any arbitrary array geometry. The emphasis in this paper is on the HLA and the limitations imposed by this type of spatial aperture, as it is a widely used sensor configuration for passive acoustic environmental monitoring.…”

Section: Introductionmentioning

confidence: 99%

“…IV, we derive the matched subspace discriminator and review the mathematics underlying the use of wave number subspace projections to enhance the observability of mode trapping on an HLA. We discuss three essential requirements: (1) The acoustic environment supports mode trapping, (2) the sensor array is deployed at a depth within, or near to, the trapping region, and (3) the source is at or near endfire orientation. A brief simulation result is presented to illustrate the concept.…”

Section: Introductionmentioning

confidence: 99%

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Use of mode subspace projections for depth discrimination with a horizontal line array: Theory and experimental results

Premus

Helfrick²

2013

The Journal of the Acoustical Society of America

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A solution to the problem of acoustic source depth discrimination in a downward refracting, shallow-water ocean waveguide is presented for the case of a horizontal line array at endfire. The approach exploits the phenomenon of mode trapping, wherein a shallow acoustic source cannot excite the lowest order waveguide modes due to its evanescent amplitude dependence near the surface. The important implication of this "trapping" behavior is that, given sufficient spatial aperture, it provides a mechanism for differentiating a shallow acoustic noise source from one at depth. The method does not require array cant, or physical vertical aperture of any kind, but instead relies only on the sensitivity of a line array at endfire to differences in horizontal wave number to resolve low and high order mode subspace excitations. The only inputs to the algorithm are an approximate sound speed profile, water depth, and bottom type. The theoretical basis for the test statistic is first reviewed, followed by discussion of key requirements, and illustration of the concept using results from a RAM PE simulation for a downward refracting environment. Finally, the algorithm is experimentally demonstrated using data from a bottom-mounted HLA deployed in the moderately cluttered continental shelf environment of the Florida Straits.

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Section: Mode Filtering With a Horizontal Line Arraymentioning

confidence: 99%

Section: Phenomenology: the Physics Of Mode Trappingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Use of mode subspace projections for depth discrimination with a horizontal line array: Theory and experimental results

Premus

Helfrick²

2013

The Journal of the Acoustical Society of America

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“…However, the frequency of the moving source must be known a priori, which is difficult with passive sonar system. Next, unlike the first approach based on depth estimation, the second approach considers depth discrimination as a binary hypothesis test; examples include the matched-subspace method [6,7], the scintillation index (SI) [8], and the trapped energy ratio [9] to improve the robustness of depth discrimination.…”

Section: Introductionmentioning

confidence: 99%

Depth Discrimination for Low-Frequency Sources Using a Horizontal Line Array of Acoustic Vector Sensors Based on Mode Extraction

Liang

Zhang

et al. 2018

Sensors

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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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Difference Factor of Vertical Beam Pattern for Shallow-Water Source Depth Discrimination

Zheng

Zhu

2021

Acoust Aust

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Mode filtering approaches to acoustic source depth discrimination

Cited by 16 publications

References 1 publication

Use of mode subspace projections for depth discrimination with a horizontal line array: Theory and experimental results

Use of mode subspace projections for depth discrimination with a horizontal line array: Theory and experimental results

Depth Discrimination for Low-Frequency Sources Using a Horizontal Line Array of Acoustic Vector Sensors Based on Mode Extraction

Difference Factor of Vertical Beam Pattern for Shallow-Water Source Depth Discrimination

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