Doubly Resonant Seismic Source for Broadband Frequency Coverage
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Solution Overview
Problem
Current low-frequency underwater sound sources for seismic operations are large, expensive, and sensitive to depth and water flow fluctuations, limiting their ability to cover a wide frequency band efficiently and requiring complex control systems for frequency modulation.
Innovation Solution
A doubly-resonant broadband seismic source using two gas-filled underwater bubble resonators tuned to different frequencies, excited by a piston driven by a linear or rotary motor, which are coupled through water to achieve a smaller, more efficient, and less sensitive sound source capable of arbitrary waveform transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single bubble resonator is used to generate low-frequency sound, then the source becomes large and expensive, but the frequency band coverage remains limited
Solution Approach 1:
The invention divides a single large resonator into multiple smaller bubble resonators (typically three), each tuned to a different frequency. This segmentation allows the system to cover a broader frequency band while keeping individual resonator sizes manageable and reducing overall system complexity and cost.
Solution Approach 2:
The invention combines multiple bubble resonators into a single integrated sound source system. The resonators are positioned close to each other and driven by a common piston, merging their acoustic outputs to produce a broadband low-frequency sound signal that would require a much larger single resonator to achieve.
2Adaptability or versatility
If a tunable bubble resonator is used to cover a large frequency band, then the dimensions become too large for standard air-gun deployment, but frequency coverage improves
Solution Approach 1:
Instead of using one large tunable resonator, the invention segments the frequency band into multiple fixed-frequency resonators. Each resonator is sized appropriately for its specific frequency range, eliminating the need for a single oversized resonator that would be required to cover the entire bandwidth.
Solution Approach 2:
The invention provides a static alternative to dynamic tuning by using multiple fixed-frequency resonators that collectively cover the desired frequency range. This eliminates the mechanical complexity and size requirements of tunable systems while maintaining broadband capability.
3Measurement precision
If a high-Q tunable resonance system is used, then frequency selectivity improves, but sensitivity to towing depth and water flow fluctuations increases
Solution Approach 1:
The invention distributes the frequency coverage across multiple resonators with moderate Q factors rather than relying on a single high-Q resonator. This segmentation reduces the sensitivity to environmental fluctuations while maintaining overall frequency selectivity through the combined response of multiple resonators.
Solution Approach 2:
The invention changes the operating parameters by using multiple resonators with slightly different frequency tuning and moderate Q factors. This parameter distribution approach reduces the sensitivity to depth and flow variations compared to a single high-Q resonator operating at a specific frequency.
4Device complexity
If a single resonator is used, then the system is simpler, but the frequency band coverage is narrow
Solution Approach 1:
The invention merges multiple simple bubble resonators into a unified system driven by a single piston. While the number of resonators increases, each resonator remains structurally simple, and the common drive mechanism maintains operational simplicity. The combined system achieves broadband coverage without requiring complex individual resonator designs.
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 results in a sound source that is smaller, cheaper, more reliable, and more powerful, with reduced sensitivity to depth and water flow fluctuations, enabling faster frequency sweeps and arbitrary waveform transmission without the need for complex control systems, suitable for frequencies as low as 1 Hz.
Implementation Method 1
a first gas filled underwater resonator permanently tuned to produce a first resonant frequency upon excitation and a second gas filled underwater resonator connected to the first resonator and permanently tuned to produce a second resonant frequency
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A sound source includes a first gas filled underwater resonator, a second gas filled underwater resonator connected to the first resonator and at least one excitation member configured to excite the first gas filled underwater resonator and the second gas filled underwater resonator, where the first gas filled underwater resonator is permanently tuned to produce a first resonant frequency upon excitation by the at least one excitation member, where the gas filled underwater second resonator is permanently tuned to produce a second resonant frequency upon excitation by the at least one excitation member, and where the first resonant frequency is different from the second resonant frequency.