Underwater Acoustic B-Scan Pre-Processing for Passive Detection
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Solution Overview
Problem
Passive detection and tracking systems struggle in noisy underwater environments due to lack of spatial processing gain, difficulty in distinguishing weak passive contacts from loud noise sources, and challenges in co-registering data with active systems, leading to spurious detections and reduced effectiveness in tracking underwater targets.
Innovation Solution
A method of pre-processing acoustic signals by generating and compressing B-scans, applying a background mask to suppress historic reflectivity and dynamic range, and analyzing A-scans to differentiate non-reverberant energy, allowing for simultaneous active and passive detection and tracking without switching between systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive detection systems use single hydrophone or small nodal collections, then the system complexity is reduced, but spatial processing gain is insufficient leading to inability to discriminate weak echo returns from stronger returns
Solution Approach 1:
The patent combines active and passive detection systems into a single integrated system, merging the receiver array used for active detection with the passive detection functionality. This allows the passive system to utilize the full spatial processing gain of the complete array rather than relying on small nodal collections, thereby improving the ability to discriminate weak echo returns while maintaining system integration.
2Ease of operation
If passive detection systems rely on contact acoustic emissions for detection, then the system operation is simplified, but detection reliability deteriorates in noisy underwater environments such as busy ports and harbours
Solution Approach 1:
The patent merges active and passive detection modes within a single system, allowing the passive detection functionality to operate alongside active detection. The integrated system can process signals from the full receiver array for both modes, enabling passive detection to benefit from spatial processing gain even in noisy environments, thereby improving reliability while maintaining operational simplicity.
3Adaptability or versatility
If active and passive detection systems are deployed independently, then each system can be optimized for its specific function, but data co-registration becomes complex and spurious detections increase
Solution Approach 1:
The patent merges active and passive detection systems into a single integrated system that processes signals through common signal processing chains. By using the same receiver array and processing architecture for both detection modes, the system eliminates the need for complex independent co-registration of data from separate systems, reducing processing complexity and minimizing spurious detections while maintaining the ability to optimize both functions.
4Measurement precision
If passive detection systems use multiple spatially distributed nodes for localisation, then localisation accuracy is improved, but installation practicality and cabling requirements deteriorate
Solution Approach 1:
The patent combines passive detection functionality with an active detection system that uses a single co-located sonar head with a full receiver array. This integration allows the passive system to achieve localisation capabilities using the same spatially distributed receiver elements as the active system, eliminating the need for separate multiple nodal installations and their associated cabling requirements, thereby maintaining localisation accuracy while improving installation practicality.
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 enhances passive detection and tracking by retaining spatial processing gains, enabling coherent tracking of low-reflectivity targets and those obscured from direct ensonification, while complementing active detection with signature-based classification, without degrading active system performance.
Implementation Method 1
This is an active system in that the surrounding water has to be ensonified to detect and track acoustic energy reflected by said contacts
Implementation Method 2
detect and track acoustic energy reflected by said contacts
Implementation Method 3
comprise a transmitter unit, a combined active/passive sonar head unit comprising a transducer array operable as both a projector and a receiver array, and a signal processing unit
Data Source
AI summary
A method of pre-processing acoustic signals received from an ensonified region (104) of an underwater environment (102) for passive detection of an object (106, 108) in the underwater environment (102). The method comprises generating (404) an acoustic B-scan (500) in respect of a predetermined time frame, and selecting (406) a temporal portion (502) of the acoustic B-scan (500) in accordance with a predetermined selection criterion. The method also comprises compressing (408) the selected temporal portion (502) of the acoustic B-scan (500) to provide a compressed acoustic B-scan (510), and applying (410) a B-scan background mask (512) to the compressed acoustic B-scan (510) to suppress any historic reflectivity samples of the compressed acoustic B-scan (510) and to provide an extant compressed acoustic B-scan (524), A dynamic range of the extant compressed acoustic B-scan (524, 600, 602, 604) is then suppressed (412).