A spiral wave front beacon for underwater navigation: transducer prototypes and testing

Area of Science:

• Underwater acoustics
• Transducer technology
• Signal processing

Background:

• Acoustic beacons are crucial for underwater navigation and positioning.
• Determining the aspect angle of a remote hydrophone is essential for accurate localization.
• Existing methods may have limitations in precise aspect determination.

Purpose of the Study:

• To experimentally investigate acoustic beacons capable of generating circular and spiral wave fronts.
• To evaluate the effectiveness of comparing circular and spiral signals for determining hydrophone aspect.
• To analyze sources of error in aspect angle measurements using these transducers.

Main Methods:

• Experimental study of transducers producing circular and spiral wave fronts.
• Utilizing a remote hydrophone to compare signal phases.
• Fabrication of 'physical-spiral' beacons using piezocomposite material and 'phased-spiral' beacons with transducer arrays.
• Laser Doppler vibrometer measurements for surface velocity analysis.

Main Results:

• Successful generation of circular and spiral wave fronts from specialized transducers.
• Demonstrated potential for aspect angle determination by comparing signal phases.
• Identified damping in piezocomposite material as a significant error source, overriding simulation-predicted discontinuity errors.
• Phase corrections were applied for hydrophones outside the horizontal plane.

Conclusions:

• Acoustic beacons with circular and spiral wave fronts offer a viable method for aspect angle determination.
• Material damping in piezocomposite transducers is a critical factor limiting measurement accuracy.
• Further research should focus on mitigating damping effects for improved performance.