Active Vibration Damper for Submarine Noise Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Military submarines and surface vehicles face challenges in minimizing structure-borne noise, which can reveal their location through waterborne vibrations, necessitating effective noise reduction measures.
Innovation Solution
The implementation of an active vibration damper system that uses a hydrophone to detect and counteract structure-borne noise by introducing phase-shifted vibrations into the support structure, ensuring destructive interference and minimal noise emission into the water environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vibration-generating devices are mounted on the supporting structure, then the submarine can perform its functions (propulsion, pumping, etc.), but structure-borne noise is transmitted to the outer hull and generates waterborne sound that can reveal the vessel's location
Solution Approach 1:
The patent applies preliminary anti-action by introducing counter-vibrations that are 180 degrees out of phase with the vibrations generated by the vibration-generating devices. The active vibration damper generates these counter-vibrations in advance to cancel out the structure-borne noise before it can significantly propagate through the supporting structure and outer hull into the water environment.
Solution Approach 2:
The patent utilizes mechanical vibration by employing an active vibration damper that generates mechanical counter-vibrations to cancel the vibrations from the vibration-generating devices. The system introduces controlled mechanical vibrations into the supporting structure that are identical in frequency and amplitude but opposite in phase to the harmful vibrations, thereby eliminating waterborne noise through destructive interference.
2Object-generated harmful factors
If active vibration dampers are introduced to compensate structure-borne noise, then waterborne noise is reduced, but the device complexity increases
Solution Approach 1:
The patent implements feedback by using a hydrophone to detect waterborne noise generated by the outer hull and feeding this information back to a control device. The control device processes the detected noise signals and adjusts the active vibration damper's counter-vibrations in real-time to optimally cancel the structure-borne noise, creating a closed-loop control system that adapts to changing noise conditions.
Solution Approach 2:
The patent uses an intermediary approach by placing the hydrophone in the water-flooded space between the outer skin and the pressure hull. This intermediate position allows the hydrophone to detect waterborne noise without being exposed to the external water environment, and the control device acts as an intermediary that processes the noise signals and coordinates the counter-vibrations from the active vibration damper.
3Measurement precision
If the hydrophone is placed outside the pressure hull to detect waterborne noise, then detection accuracy is improved, but the hydrophone is exposed to external environmental influences
Solution Approach 1:
The patent applies the nested doll principle by placing the hydrophone in the water-flooded space between the outer skin and the pressure hull. The hydrophone is nested within the protective structure of the submarine, specifically in the annular space created by the double-hull design. This nested position allows the hydrophone to be surrounded by water for accurate noise detection while being protected from external environmental influences by the outer skin and pressure hull structure.
Solution Approach 2:
The water-flooded space between the outer skin and pressure hull serves as an intermediary environment for the hydrophone. This intermediate space allows the hydrophone to be exposed to water for detecting waterborne noise while being shielded from direct external environmental influences such as pressure, temperature extremes, and physical damage by the surrounding hull structure.
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 significantly reduces or eliminates waterborne noise, enhancing the stealth capabilities of submarines and surface vehicles by canceling out vibrations through controlled counter-vibrations, thereby minimizing detectability.
Implementation Method 1
the vibration energy introduced into the supporting structure by the vibration-generating devices is at least partially compensated by introducing vibrations into the supporting structure which largely and, in the best case, completely cancel out the vibrations introduced into the supporting structure by the vibration-generating devices by means of destructive interference
Implementation Method 2
The hydrophone precisely detects the noise emanating from the outer hull due to its structure-borne sound excitation, which propagates over long distances in the water
Data Source
Figure 1~2
AI summary
The invention relates to a watercraft comprising a support structure that is in contact with the ambient water. Said watercraft comprises means for compensating structure-borne noise in the support structure and a hydrophone located in the water surrounding the watercraft. The hydrophone is signal-connected to a device for controlling the means for compensating structure-borne noise.