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The parameters of deep ocean sediments are relevant for accurately predicting the sound field; however, it is difficult to measure the parameters in situ. Most inversion methods used in shallow water are inapplicable in the deep ocean because of the considerable differences in propagation characteristics. At present, no method for simultaneously obtaining sound speed, density, and attenuation that...
The noise spatial correlation coefficient between two array elements deployed vertically in real deep ocean environment is not consistent with that in isotropic ambient noise field because of surface-distributed wind driven noise sources. Therefore, it is necessary to analyze the performance of vertical line array spatial gain properly. A method for modeling wind-driven ambient noise field is described...
Cylindrical arrays are widely used in sonar systems for underwater target detection. For the sake of reducing calculation, each line of hydrophones at the same azimuth direction aligned with the cylinder axis are hardwired together in practice and thus, each line array with omnidirectional sensors becomes a directional sensor steered to broadside. As a result, the cylindrical array can be treated...
In this study, the conventional beamforming (CBF) and the minimum variance distortionless response (MVDR) beamforming with a line hydrophone array mounted on an infinite rigid cylindrical baffle are proposed. Based on decomposing the sound field into a summation of harmonics, a model is introduced to compute the noise cross-spectral matrix in the spherically isotropic noise field. Some design examples...
Understanding the physical features of the flow noise for hydrophones in a fluid-filled towed array is important for designing a towed line array sonar. The flow noise of hydrophones in fluid-filled towed arrays generated by the turbulent pressure is derived by the frequency–wave number decomposition method. The results show that the flow noise increases rapidly with the towed speed and decreases...
The received wind driven noise field can be described as a sum of fields radiated from many random sources on the sea surface. Wind driven noise source levels can be modeled by empirical relationship with local wind speed. A method for modeling wind-driven ambient noise based on ray approach in deep ocean is presented. Simulations are performed to demonstrate the validity of the method. The wind-driven...
A method of estimating the source depth of wideband underwater acoustic pulses in deep water is proposed in this paper. The method is based on the characteristic of frequency domain interference oscillation of broadband signals received at a single stationary hydrophone. The oscillation period is related to the Lloyd's Mirror effect (LME) and can be transformed into the information of source depth...
The internal solitary waves propagating over the shelf slope fluctuating the acoustic energy in shallow water has been widely studied. In this paper, this process is broadened into the continental slope with different gradient at different range which is linked with the shallow water and the deep water. The temporal and spatial structures of the acoustic field with the internal solitary wave passing...
This paper presents a single-hydrophone based method for source range localization from information contained in the multipath propagation in the reliable acoustic path (RAP) environment. The time delays between the direct (D) and the surface-reflected (SR) arrivals are obtained from the autocorrelation of the received signal and are compared with the D-SR time delays predicted by the acoustic model...
An ensemble Kalman filter (EnKF) approach is proposed to perform sequential tracking of water column sound speed profile (SSP) using a moving acoustic source. First, the SSPs are discretized in depth and range, and are expressed by the empirical orthogonal functions (EOFs). Second, the acoustic source state information and the first three orders of EOF coefficients are expressed as the state variable,...
Waveguide sound propagation in continental slope with a varying-gradient water-sediment interface and special environment is very complex. Given three different gradients for shelf break areas and a defined gradient for the continental slope, numerical simulations with a full-wave range-dependent acoustic model show that the energy distributes distinctly in different depth in the sound field, in which...
This paper studies and discusses robust minimum variance distortionless response (MVDR) beamformer with subarray multistage processing for circular hydrophone arrays, which is an extension of the multistage MVDR beamformer with line microphone arrays for noise reduction. The basic theory is to divide the hydrophones into a certain number of groups with each group only having two hydrophones for MVDR...
Underwater sensors will diverge from the initial position because of the ocean current when the underwater sensors are deployed in the deep ocean. Assuming that the xy-plane coincides with the sea surface, a local Cartesian x-y coordinates system is set up in such a way that, when the sensors and sources are projected onto the local xy-plane, its origin coincides with the initial point of the sensors...
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