Symmetrical Piston Sound Projector for Marine Seismic Arrays
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Solution Overview
Problem
Marine seismic surveys using impulsive sound sources, such as air guns, pose environmental concerns due to high-energy sound waves that can be detrimental to marine life, and existing coherent sound sources have not been widely adopted due to technical challenges in achieving accurate imaging and efficient energy distribution.
Innovation Solution
A piston-type sound projector employing an electro-magnetic driver with a moving armature force generator, utilizing a symmetrical magnetic circuit and feedback control systems to produce time-harmonic waveforms, which are distributed in arrays to minimize reaction loads and ensure accurate seismic imaging while avoiding cavitation and out-of-band noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If air guns are used to generate high-energy sound waves for seismic surveys, then source level and penetration depth are improved, but environmental harm to marine life increases
Solution Approach 1:
The patent replaces the pneumatic system (air gun) with an electromagnetic system. The electromagnetic driver uses a voice coil and permanent magnet assembly to directly drive the piston, eliminating the need for high-pressure air discharge. This substitution allows for coherent, controlled sound wave generation without the impulsive, high-energy bursts that harm marine life, while maintaining adequate source levels for seismic imaging.
Solution Approach 2:
The patent changes the temporal and spectral parameters of sound generation. Instead of impulsive, broadband sound waves from air guns, the electromagnetic piston system generates coherent, continuous sound waves with controlled frequency content. The sound waves are concentrated in the 10-100 Hz range, avoiding high-frequency components that are particularly harmful to marine life, while maintaining sufficient energy for deep penetration through the use of long-duration sweeps.
2Object-affected harmful factors
If coherent sound sources are used to reduce environmental impact, then energy distribution over time is improved, but source level and imaging accuracy deteriorate
Solution Approach 1:
The patent employs a dynamic electromagnetic driver system that can rapidly adjust its output. The voice coil and permanent magnet assembly enable precise control over piston motion, allowing the system to generate high-amplitude coherent waves when needed while maintaining environmental benefits. The system can dynamically modulate the sound wave characteristics to achieve both high source levels and low environmental impact through optimized sweep signals and frequency control.
Solution Approach 2:
The patent uses periodic electromagnetic driving to generate coherent sound waves. The electromagnetic driver operates in a controlled periodic manner, using sine wave or sweep signals to drive the piston back and forth. This periodic action produces continuous, coherent sound waves that distribute energy over time (reducing peak intensity and environmental harm) while maintaining sufficient average power for deep penetration and accurate imaging through extended survey times.
3Force
If electromagnetic driver with symmetrical magnetic circuit is used, then reaction loads are reduced, but device complexity increases
Solution Approach 1:
The patent employs a symmetrical magnetic circuit design where the permanent magnet assembly is positioned to create balanced magnetic fields on both sides of the piston. This symmetry causes the reaction forces generated during electromagnetic driving to cancel each other out, significantly reducing net reaction loads on the transducer housing and mounting structure. The symmetrical arrangement of magnetic poles and coil windings ensures that forces are evenly distributed, simplifying the mechanical support requirements despite the increased magnetic circuit complexity.
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 provides a coherent sound source that reduces environmental impact by distributing energy over a longer period, enhances seismic survey accuracy, and maintains low-frequency sound levels, thereby minimizing harm to marine life while achieving high source levels and precise control over sound waves.
Implementation Method 1
an electro-magnetic force generator substantially having mechanical and magnetic symmetry about its geometric center
Implementation Method 2
producing time-harmonic waveforms... two pistons positioned on either side of a single electro-magnetic force generator
Data Source
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AI summary
A coherent sound source is provided for marine seismic surveys. An underwater sound projector for producing time-harmonic waveforms comprises two pistons positioned on either side of a single electro-magnetic force generator substantially having mechanical and magnetic symmetry about its geometric center to substantially cancel reaction loads that occur when the pistons are actuated. The underwater sound projector optionally also includes control systems to improve the fidelity of the force generator, provide pressure compensation to the pistons, finely adjust the static position of the pistons, and change the depth and roll when it is configured as tow body. A plurality of underwater sound projectors can be configured in an array. A load-bearing umbilical can connect the underwater sound projectors to a ship, transmit electrical power to each array element and serve as a duplex data transmission medium to route commands from the ship to the projector and report machinery status.