Date of Award

2023

Publication Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

Keywords

Underwater signal processing, Selective multi-modal pair, Remote monitoring

Supervisor

M.Saif

Supervisor

J.Ahamed

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

Applications of underwater signal processing are essential for environmental monitoring. Remote monitoring and passive sound source localization in an underwater environment can provide great insight into geological studies, environmental changes and marine lives monitoring. While various methods are available for Localization, they mostly employ arrays of hydrophones, requiring synchronization or prior knowledge of the source signals, which can prove costly, complicated, and hard to maintain. Remote monitoring applications require very high-range passive localization methods; and, given the frequency-selective nature of ambient noise and other channel parameters, current localization methods have short-distance range estimation or high localization error for long distances. The modal analysis makes it possible to study and localize sounds propagated over long distances using one passive hydrophone without a need for prior knowledge of the source or synchronization. This dissertation presents four new stand-alone multi/single hydrophone localization algorithms based on modal dispersion analysis to localize impulsive sound sources in a noisy shallow water environment. The first algorithm is named as selective multi-modal pair (SMP), enables utilizing modals with any wavenumbers as opposed to previously proposed methods based on only on the modes with sequential wavenumbers. The algorithm extracts the dispersion curves of the received signal to be compared against the dispersion curves computed using a custom channel. then chooses the most effective modes (that result in the lowest localization error) , estimated the range of a sound source. The resulting estimated range is the range that makes the best match between the selected modal dispersion curves and the estimated dispersion curves. Numerical results, using both simulated and actual recorded sounds of whale and underwater explosion show that the proposed algorithm can localize underwater sounds with high accuracy when the signal-to-noise ratio varies from 28dB to 45dB. The second Localization algorithm is named selective weighted genetic algorithm (SW-GA). This algorithm employs two weighting functions based on geolocation information of the source and a selective scaling function for the selection of the most noise resistive modal pairs. The proposed weighted localization scaling and selection functions are designed to ensure convergence towards the correct range estimation. We analyzed and compared this algorithm using the same signals and SNR scenarios as before and shows a better2D localization performance and noise resistivity compared with previously proposed methods. The third and fourth algorithms, named Weighted Multi-Modal (WMM)and Multi-Modal (MM) employs all available modal pairs instead of just a few or a sequential selection. They compute a modal contribution matrix based on all available modal pairs with common frequencies. Furthermore, the weighted version of the algorithm employs the contribution matrix for assigning weights based on contribution/noise resistivity to all modal pairs. Employing all available modes results in an algorithm capable of localizing signals with higher frequencies and the weighting function increase accuracy in low SNR environments. The noise performance analysis of both the WMM algorithm; and the non-weighted version yields considerable improvements in localization of sound sources in the presence of high level of ambient noise over other algorithms used in this work.

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