Acoustic B-scan Filtering for Underwater Passive Detection
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Solution Overview
Problem
Current passive detection and tracking systems in underwater environments struggle to effectively detect and track weakly emitting targets in noisy conditions due to lack of spatial processing gain and interference from active sonar systems, leading to spurious detections and reduced operational efficiency.
Innovation Solution
A method for filtering acoustic B-scans to enhance passive detection and tracking by pre-processing signals to remove historic artefacts and reverberant energy, scoring energy content, and applying criteria to identify potential sources of non-reverberant energy, allowing for contemporaneous active and passive detection using common hydrophone hardware and bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive detection systems use single hydrophone or small nodal collections, then device complexity is reduced, but spatial processing gain is insufficient leading to inability to detect weakly emitting targets in noisy environments
Solution Approach 1:
The patent combines active and passive detection systems into a single integrated system that shares common hydrophone hardware and signal processing resources. The active sonar provides ensonification and spatial processing gain, while the passive system detects acoustic emissions from targets. By merging these systems, the patent achieves sufficient detection capability for weakly emitting targets without requiring separate large-scale passive arrays, thus resolving the contradiction between device complexity and measurement precision.
2Reliability
If active sonar systems operate continuously, then target detection capability is maintained, but interference with passive detection increases causing spurious detections
Solution Approach 1:
The patent implements periodic switching between active and passive detection modes. The system alternates between active sonar ensonification cycles and passive listening periods, allowing passive detection to occur during intervals when active transmission is not occurring. This periodic operation reduces interference from active sonar while maintaining target detection capability, resolving the contradiction between detection reliability and interference levels.
Solution Approach 2:
The patent introduces sophisticated signal processing as an intermediary that distinguishes between active sonar reverberation and passive acoustic emissions from targets. By analyzing signal characteristics, temporal patterns, and spatial distribution, the system can separate genuine passive emissions from active sonar interference, enabling reliable passive detection even during active operation and reducing spurious detections.
3Measurement precision
If passive systems rely on multiple spatially distributed nodes for localization, then measurement precision improves, but device complexity and installation requirements increase significantly
Solution Approach 1:
The patent makes the common hydrophone array universal by enabling it to perform both active sonar functions (transmission and reception for range-bearing localization) and passive detection functions (reception of acoustic emissions). The same hardware infrastructure supports multiple detection modes and provides spatial processing gain for both active and passive operations, eliminating the need for separate distributed passive nodes and reducing installation complexity while maintaining localization accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables enhanced passive detection and tracking with retained spatial processing gains, co-registered tracking between active and passive systems, and the ability to track low reflectivity targets without switching between systems, improving target classification and reducing interference.
Implementation Method 1
receiving acoustic signals from the ensonified region of the underwater environment
Implementation Method 2
acoustic energy reflected by said contacts
Implementation Method 3
pre-processing the acoustic B-scan to remove historic artefacts and mitigate influence of reverberant energy
Data Source
AI summary
A method of filtering an acoustic B-scan (500) for passive detection of an object (106, 108) underwater comprising ensonifying (400) a region (104) of an underwater environment (102) and receiving (402) acoustic signals from the ensonified region (104) of the underwater environment (102), the received acoustic signals corresponding to a plurality of sonar beams. The method also comprises generating (404) the acoustic B-scan (500) from the received acoustic signals and pre-processing (406-414) the acoustic B-scan (500) to remove historic artefacts and mitigate influence of reverberant energy. Energy content is then scored (416) in respect of the pre-processed acoustic B-scan (524) to provide a plurality of energy scores and at least one local maximum (200) of the plurality of energy scores is; identified (418). A predetermined criterion is then applied (808) to a local maximum (700) of the at least one local maximum (700) identified.