Hydrophone with Dilatant Coupling for Static Pressure Isolation
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Solution Overview
Problem
Existing hydrophone arrays for underwater acoustic sensing are susceptible to detection due to local active instrumentation and data/power cabling, and fibre optic-based hydrophones face performance issues at depth due to lack of depth pressure compensation, causing saturation and failure to detect dynamic pressure signals.
Innovation Solution
A hydrophone design incorporating a pressure-bearing element, a motion sensor, and a dilatant coupling material that mechanically transmits dynamic pressure while isolating static pressure, using a frequency-dependent viscosity profile to filter out low-frequency static pressure movements, and a fibre optic cable with a laser active region that varies wavelength with mechanical strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fibre optic technology is used for hydrophones, then detection susceptibility and device complexity are reduced, but measurement precision deteriorates at depth due to static pressure saturation
Solution Approach 1:
The hydrophone is segmented into distinct functional components: a pressure-bearing element (membrane) that selectively transmits dynamic pressure, a dilatant coupling material that filters static pressure, and a motion sensor that detects only dynamic pressure movements. This segmentation allows each component to perform its specific function optimally, resolving the contradiction between simplified fibre optic design and maintained measurement precision at depth.
Solution Approach 2:
A dilatant coupling material is introduced as an intermediary between the pressure-bearing element and the motion sensor. This intermediary selectively transmits dynamic pressure while blocking static pressure, enabling the fibre optic sensor to maintain measurement precision at depth without requiring complex active instrumentation or depth compensation systems.
2Ease of operation
If fibre optic hydrophones are deployed at depth, then deployment flexibility is improved, but measurement precision deteriorates due to static pressure saturation
Solution Approach 1:
The hydrophone employs passive depth compensation through the inherent properties of the dilatant coupling material, which automatically filters static pressure based on its frequency-dependent viscosity characteristics. This self-service mechanism eliminates the need for active depth compensation systems, maintaining measurement precision while preserving the deployment flexibility and simplicity of passive fibre optic hydrophones.
3Measurement precision
If active instrumentation and cabling are used in hydrophone arrays, then measurement precision is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The invention extracts and eliminates the need for active instrumentation, data cabling, and power cabling from the hydrophone array system. By using passive fibre optic sensors combined with the dilatant coupling material's selective pressure transmission, the system achieves adequate measurement precision without the complexity and operational difficulties associated with active electronic components.
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
The solution effectively compensates for depth-dependent static pressure, enhancing the detection of dynamic pressure signals and reducing the need for excessive optical bandwidth, thereby improving the performance and deployability of underwater acoustic sensors.
Implementation Method 1
a dilatant coupling material disposed intermediate said pressure-bearing element and said motion sensor so as to mechanically transmit movements substantially corresponding to said dynamic pressure from said pressure-bearing element to said motion sensor, said dilatant coupling material not transmitting movements to said motion sensor that substantially correspond to said depth-dependent static pressure
Implementation Method 2
the dilatant coupling material has a mechanical strain frequency dependent viscosity profile
Implementation Method 3
a fibre optic cable having a laser active region defining an emitted wavelength varying in accordance with a mechanical strain acting on the laser active region
Implementation Method 4
the motion sensor is a piezoelectric sensing ceramic
Data Source
Figure 1~2
Figure 3~4
AI summary
A hydrophone (10) for immersion in a liquid body defining a depth-dependent static pressure and a dynamic pressure. The hydrophone (10) includes a pressure-bearing element (11) for exposure to the liquid body; a motion sensor (13) spaced apart from the pressure bearing element (11); and a dilatant coupling material (14) disposed intermediate the pressure-bearing element (11) and the motion sensor (13) so as to mechanically transmit movements substantially corresponding to the dynamic pressure from the pressure-bearing element (11) to the motion sensor (13). The dilatant coupling material (14) does not transmit movements to the motion sensor (13) that substantially correspond to the depth-dependent static pressure.