The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
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...
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...
This paper presents a method of direction-of-arrival estimation using the high-order superdirective beamforming for a circular hydrophone array. The weighting vectors with different orders used for DOA estimation can be obtained using the previously proposed eigenbeam decomposition and synthesis theory, which can provide frequency-invariant beampatterns in a wide frequency band. The DOA estimation...
This paper first presents a superdirective frequency-invariant beamforming method for circular sensor arrays. The weighting vector of this method is in close-form, which is derived using the criterion of minimizing the mean square error between the desired and synthesized beampatterns. A detailed experimental study of this superdirective frequency-invariant beamforming method is then followed, which...
In this paper, Argo data combined with altimetry data were used to investigate the effect of eddy on Sound Speed Profile (SSP) in Northwestern Pacific Ocean. A combination of the closed contours method and the Okubo-Weiss method is used to detect the eddy. Statistics of SSP anomalies induced by eddy have been calculated by removing the climatology from Argo profiles in eddy. Then effects of eddy on...
Ocean ambient noise mainly includes uncorrelated noise and correlated noise. The uncorrelated noise only affects the diagonal elements in the noise covariance matrix, and it can be suppressed by subtracting a value on the diagonal elements. Utilizing this feature, a high array-gain beamforming based on diagonal reducing is presented. Meanwhile, the robustness becomes poor. So, the array weight norm...
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...
This paper studies the effects of hydrophone gain errors and self-noise on the direction-of-arrival (DOA) performance of three methods: the conventional beamforming (CBF) method, the minimum variance distortionless response (MVDR) method and the multiple signal classification (MUSIC) method. Simulations for a 16-hydrophone uniform circular array whose diameter is 2 m are provided in three different...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.