Multi-Resonance Flextensional Acoustic Projector Stave Design
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Solution Overview
Problem
Existing low frequency acoustic projectors are limited by their single resonance vibration mode, which restricts their operation to a narrow frequency band, and they are also susceptible to changes in acoustic characteristics due to hydrostatic pressure variations.
Innovation Solution
A multi-resonance flextensional low frequency acoustic projector is designed with a piezoelectric actuator and a plurality of staves configured in different shapes to generate two or more resonance vibration modes, allowing for broadband frequency transmission and resistance to hydrostatic pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single resonance vibration mode is used in the stave, then the device structure is simple, but the frequency bandwidth is narrow
Solution Approach 1:
The stave is divided into multiple segments along its length, with each segment having different geometric parameters (thickness, width, curvature). This segmentation allows each portion to contribute to different resonance modes, enabling the entire stave to support multiple vibration modes simultaneously while maintaining a single integrated structure.
Solution Approach 2:
Different portions of the stave are designed with locally optimized geometric properties. The thickness, width, and curvature vary along the length of the stave, creating local variations in stiffness and mass distribution. This local quality variation enables the stave to exhibit multiple resonance frequencies and vibration modes, expanding the operational bandwidth.
2Ease of manufacture
If a flat radiating plate is used, then the manufacturing is simple, but the low-frequency operation with small size is difficult
Solution Approach 1:
The radiating plate is designed with a curved surface rather than a flat geometry. This curvature modifies the bending stiffness distribution across the plate, enabling more effective low-frequency vibration modes. The curved shape allows the plate to achieve the necessary flexibility for low-frequency operation while maintaining a compact size, avoiding the need for a large flat plate.
3Reliability
If air-backing is provided for the radiating plate, then the acoustic radiation is effective, but the acoustic characteristics change with hydrostatic pressure
Solution Approach 1:
The air-backing cavity is completely removed from the projector structure. Instead of providing acoustic energy storage and radiation enhancement through an air-filled backing space, the invention uses the curved radiating plate itself and the surrounding water medium to achieve effective acoustic radiation. This elimination of the air-backing system prevents the hydrostatic pressure-induced changes in acoustic characteristics while maintaining radiation efficiency.
Solution Approach 2:
The mechanical air-backing system is replaced with a direct water-coupled vibration system. The radiating plate vibrates directly in contact with the water medium, utilizing the water's acoustic properties instead of relying on an air cavity. This substitution eliminates the compressibility issues associated with air under hydrostatic pressure while maintaining effective acoustic energy transfer to the water.
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 multi-resonance projector achieves low frequency acoustic transmission across a wide frequency band while minimizing changes in acoustic characteristics under varying hydrostatic pressures, enabling more effective underwater communication and detection.
Implementation Method 1
a piezoelectric actuator that generates longitudinal vibration
Implementation Method 2
a plurality of staves attached to an outer surface of the piezoelectric actuator to convert longitudinal vibration generated by the piezoelectric actuator into lateral vibration perpendicular to the outer surface of the piezoelectric actuator
Implementation Method 3
Since lateral vibration utilizes a bending mode of the radiating plate, rigidity of the radiating plate may be relatively lowered, and thus low-frequency operation of the projector is possible with a small size
Data Source
AI summary
A multi-resonance flextensional low frequency acoustic projector of the present disclosure includes a piezoelectric actuator; a plurality of staves attached to an outer surface of the piezoelectric actuator to convert longitudinal vibration generated by the piezoelectric actuator into lateral vibration perpendicular to the outer surface of the piezoelectric actuator; and an acoustic window surrounding an exterior of the staves and water-tightening the inside of the projector. The plurality of staves is configured in shapes different from each other to generate two or more types of resonance vibration modes, so there is an effect of allowing low frequency acoustic transmission in a wide frequency band.