Spatial audio signal processing for passive sonar applications
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School of Electrical Engineering |
Doctoral thesis (article-based)
| Defence date: 2024-09-20
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Authors
Bountourakis, Vasileios
Date
2024
Department
Informaatio- ja tietoliikennetekniikan laitos
Department of Information and Communications Engineering
Department of Information and Communications Engineering
Major/Subject
Mcode
Degree programme
Language
en
Pages
68 + app. 72
Series
Aalto University publication series DOCTORAL THESES, 140/2024
Abstract
This thesis consists of five publications that focus on the development and evaluation of techniques designed for passive sonar applications utilising hydrophone arrays. The research specifically explores the topic of underwater soundfield visualisation on the horizontal plane for bearing estimation and tracking of sound-emitting targets. The explored techniques draw their inspiration from established microphone array techniques, widely adopted in the field of spatial audio, presenting novel approaches to traditional localisation problems in the underwater domain. In particular, the first publication proposes a novel spatial post-filter in the circular harmonic domain suitable for application in large circular hydrophone arrays, similar to those found in modern submarines. This proposed post-filter is essentially an extension of the Cross-Pattern Coherence (CroPaC) post-filter to higher orders of circular harmonics. The second and third publications concern the development of a space-domain version of CroPaC, i.e., a version that operates directly on the hydrophone array signals, eliminating the need for conversion into the circular harmonic domain. This aspect holds particular significance for passive sonar, as it enables the application of CroPaC to linear arrays, which are the predominant type of arrays used in underwater acoustics. The fourth publication proposes a novel approach for underwater soundfield visualisation using circular hydrophone arrays. The proposed approach is inspired by the soundfield analysis performed in Higher-Order Directional Audio Coding (HO-DirAC), a parametric spatial audio technique which extracts spatial parameters from directionally constrained regions termed sectors. Finally, the fifth publication proposes the use of an optimal mass transport framework for bearing estimation and tracking of underwater targets, achieved by solving a convex optimisation problem. The evaluation of the techniques was conducted using hydrophone array data obtained from highly detailed numerical simulations as well as real-world hydrophone array recordings. The examined array types include linear arrays with both baffled and open designs, as well as circular arrays mounted on cylindrical baffles. In the majority of cases, the array designs were chosen to align with specifications of arrays commonly used in passive sonar operations with submarines. The performance of the proposed techniques demonstrated significant improvements over conventional passive sonar techniques in many cases. These improvements pertain to the accuracy of bearing estimation, the side-lobe suppression capability, the separation of closely spaced targets, the computational complexity, and the robustness to noise, interference, and model mismatch. Lastly, it is noted that, while the evaluation primarily focused on specific hydrophone arrays of special interest deployed in shallow-water environments, the results have broader applicability and may therefore be generalised to other use cases.Description
Supervising professor
Pulkki, Ville, Prof., Aalto University, Department of Information and Communications Engineering, FinlandThesis advisor
Pulkki, Ville, Prof., Aalto University, Department of Information and Communications Engineering, FinlandKeywords
spatial audio, hydrophone array processing, passive sonar
Other note
Parts
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[Publication 1]: Vasileios Bountourakis, Leo McCormack, Mathias Winberg, Ville Pulkki. Parametric spatial post-filtering utilising high-order circular harmonics with applications to underwater sound-field visualisation. The Journal of the Acoustical Society of America, Volume 149, issue 6, pages 4463-4476, June 2021.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202107017820DOI: 10.1121/10.0005414 View at publisher
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[Publication 2]: Vasileios Bountourakis, Leo McCormack, Ville Pulkki. Spatial post-filter for linear hydrophone arrays with applications to underwater source localisation. JASA Express Letters, Volume 2, issue 8, pages 4463-4476, August 2022.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202301021025DOI: 10.1121/10.0013753 View at publisher
- [Publication 3]: Vasileios Bountourakis, Ville Pulkki. Cross-pattern coherence spatial filtering with hydrophone arrays for passive-sonar applications. In Proceedings of the 24th International Congress on Acoustics (ICA2022), Gyeongju, Korea, October 2022. https://www.ica2022korea.org/data/Proceedings_A19.pdf
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[Publication 4]: Vasileios Bountourakis, Ville Pulkki. Underwater soundfield visualization using directionally constrained acoustic parameters. The Journal of the Acoustical Society of America, Volume 154, issue 5, pages 3259–3275, November 2023.
DOI: 10.1121/10.0022443 View at publisher
- [Publication 5]: Vasileios Bountourakis, Filip Elvander, Ville Pulkki. Using optimal mass transport in bearing-time records for underwater target localization and tracking. In Proceedings of the 7th Underwater Acoustics Conference & Exhibition (UACE2023), Kalamata, Greece, June 2023