Near-Field Acoustic Measurements Using a Line Array in Shallow Water

2012 ◽  
Author(s):  
D. C. Barber ◽  
David L. Bradley
Keyword(s):  
Shallow Water ◽  
Near Field ◽  
Acoustic Measurements ◽  
Line Array

Sound speed profile inversion using a horizontal line array in shallow water

2014 ◽  
Vol 58 (1) ◽  
pp. 1-7 ◽  
Author(s):  
ZhengLin Li ◽  
Li He ◽  
RenHe Zhang ◽  
FengHua Li ◽  
YanXin Yu ◽  
...  
Keyword(s):  
Shallow Water ◽  
Sound Speed ◽  
Horizontal Line ◽  
Speed Profile ◽  
Sound Speed Profile ◽  
Line Array ◽  
Profile Inversion

scholarly journals Method to Determine the Far-Field Beam Pattern of A Long Array From Subarray Beam Pattern Measurements

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1236
Author(s):  
Donghwan Jung ◽  
Jeasoo Kim
Keyword(s):  
Conventional Method ◽  
Field Condition ◽  
Near Field ◽  
Plane Waves ◽  
Measurement Data ◽  
Beam Pattern ◽  
Far Field ◽  
Water Tank ◽  
Discrete Line ◽  
Line Array

Beam pattern measurement is essential to verifying the performance of an array sonar. However, common problems in beam pattern measurement of arrays include constraints on achieving the far-field condition and reaching plane waves mainly due to limited measurement space as in acoustic water tank. For this purpose, the conventional method of measuring beam patterns in limited spaces, which transform near-field measurement data into far-field results, is used. However, the conventional method is time-consuming because of the dense spatial sampling. Hence, we devised a method to measure the beam pattern of a discrete line array in limited space based on the subarray method. In this method, a discrete line array with a measurement space that does not satisfy the far-field condition is divided into several subarrays, and the beam pattern of the line array can then be determined from the subarray measurements by the spatial convolution that is equivalent to the multiplication of beam pattern. The proposed method was verified through simulation and experimental measurement on a line array with 256 elements of 16 subarrays.

Towards a Lateral Line Sensor to Supplement Sonar in Shallow Water

2014 ◽  
Author(s):  
Tim Ziemer
Keyword(s):  
Shallow Water ◽  
Lateral Line ◽  
Near Field ◽  
Sensory System ◽  
Digital Signal ◽  
Detection Methods ◽  
Whole Body ◽  
Water Displacement ◽  
Marine Animals ◽  
Passive Sonar

Sonar provides vessels with a sensory system to detect and identify still and moving obstacles. In shallow water both active and passive sonar meet their limits. Acoustical methods exist, aiming at supporting sonar systems by means of digital signal processing, or, coming from the field of biomimetics, imitating echolocation principles of marine animals. This paper introduces a sensor system combining these approaches by the use of a vector sensor array applying Near-field Acoustical Holography (NAH) imitating the Lateral Line organ (LL) of fish; a passive method to supplement active and passive sonar. LL is able to localize obstacles due to their dipole-like water displacement by comparing low-frequency water accelerations distributed along the whole body. In contrast to pressure, accelerations are highly evanescent and do not propagate into the far-field. Thus LL does not suffer under reverberation or scattering. The performance of the proposed NAH-based LL-sensor is tested by a computer simulation of a source in absence and in presence of a disturbing source. The LL-sensor has proven to be more robust than pressure detection methods like beamforming and conventional NAH.

Vertical line array beamforming of signal and noise in shallow‐water regions

2004 ◽  
Vol 116 (4) ◽  
pp. 2535-2535
Author(s):  
Tim Duda ◽  
James Lynch ◽  
Phil Abbot ◽  
Ruey‐Chang Wei
Keyword(s):  
Shallow Water ◽  
Vertical Line ◽  
Line Array ◽  
Array Beamforming

Uses of near-field hydrophone measurements for shallow-water imaging and demultiple

2016 ◽  
Author(s):  
Haiyang Wang ◽  
John Anderson ◽  
Michael Norris ◽  
Young Ho Cha
Keyword(s):  
Shallow Water ◽  
Near Field

MULTIPLICATIVE PADÉ PE FORMULATION APPLIED TO SWAM'99 TEST CASES

2001 ◽  
Vol 09 (01) ◽  
pp. 227-241 ◽  
Author(s):  
WOOJAE SEONG ◽  
BYUNGHO CHOI
Keyword(s):  
Parabolic Equation ◽  
Shallow Water ◽  
Environmental Changes ◽  
Near Field ◽  
Acoustic Propagation ◽  
Acoustic Modeling ◽  
Test Cases ◽  
Underwater Sound ◽  
Depth Direction ◽  
National University

Accurate forward modeling of acoustic propagation is crucial in underwater sound applications that rely on coherent field predictions, such as source localization and geoacoustic inversion based on matched field processing concepts. As acoustic propagation in shallow water environments becomes important in recent years, range-dependent modeling due to environmental changes has to be considered of which parabolic equation (PE) method has received widespread use because they are accurate and relatively fast. In this paper, Seoul National University parabolic equation (SNUPE) employing a multiplicative Padé formulation is developed. Linearization of the depth direction operator is achieved via expansion into a multiplication form of Padé approximation. To approximate the depth directional equation, Galerkin's method is used with partial collocation to achieve computational efficiency. To approximate the range directional equation, Crank–Nicolson's method is used. Finally, numerical self-starter has been used to initiate the near-field solution. The Shallow Water Acoustic Modeling (SWAM'99) Workshop provides an opportunity to test SNUPE's accuracy and compare its results with others for a variety of synthetic environments. In this paper, the numerical implementation and accuracy of SNUPE is tested by comparing with RAM12 results for the SWAM'99 test cases. Numerical experiments for SWAM'99 test cases give satisfactory results in accuracy for SNUPE and show the importance of the bottom information in the shallow water acoustic modeling.

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