Application Cases

Introduction

Ultra-low-frequency underwater acoustic transducers serve as critical hardware for ocean geacoustic inversion, ocean acoustic thermometry, long-range underwater acoustic communication and underwater acoustic countermeasure applications. When carried by unmanned underwater vehicles (UUVs), conventional electrodynamic transducers suffer from extremely low electro-acoustic efficiency within the sub-100 Hz band. Such low efficiency brings excessive energy consumption and greatly shortens the continuous mission duration of UUV platforms. Existing improvement approaches mainly focus on impedance matching and magnetic circuit optimization, while few studies target the inherent low-radiation-resistance bottleneck under ultra-low-frequency conditions, which creates an urgent demand for new transducer design schemes to boost acoustic radiation performance for battery-powered underwater carriers.

The prototype experiments and finite-element simulations in this work respond to the above practical requirements for UUV-borne underwater acoustic equipment. A multi-vibrator electrodynamic transducer prototype utilizing mutual-radiation coupling effect is designed, manufactured and tested in an anechoic water tank. Comparative tests between single-vibrator and six-vibrator prototypes verify that mutual-radiation interaction can raise radiation resistance, so as to realize substantial promotion in radiated acoustic power, electro-acoustic efficiency and transmitting-current response. The experimental findings are well consistent with theoretical predictions. This research provides feasible theoretical support and hardware references for developing high-efficiency ultra-low-frequency sound sources applicable to energy-limited underwater unmanned platforms, and the technical idea can also be extended to the design of other underwater acoustic transducers.

Research Direction

Underwater Acoustic Transducer

Experimental objective

To verify the effectiveness of the multi-element mutual radiation theory in improving the electroacoustic efficiency of ultra-low-frequency electrodynamic transducers, two electrodynamic transducer prototypes were designed and fabricated: a single-element transducer and a six-element transducer. Through comparative experiments, the influence of the multi-element transducer structure on the radiated acoustic power, electroacoustic efficiency, and transmitting current response of the transducer was investigated. The same test system was used to test the acoustic radiation performance of both prototypes in the ultra-low frequency band below 100 Hz, with a focus on verifying the role of the mutual radiation effect in improving electroacoustic efficiency and transmitting response performance.

Testing equipment

ATA-63120 power amplifier, signal source, filter, oscilloscope, etc.

Experimental process

A test system was set up in an anechoic water tank (as shown in the figure below). The signal source generates a sinusoidal excitation signal, which is amplified by the ATA-63120 power amplifier to drive the electrodynamic transducer prototype. A hydrophone is used to receive the radiated acoustic signal, which is filtered and gain-adjusted by a filter and then displayed on an oscilloscope for reading. In the ultra-low frequency band below 100 Hz, the transmitting current response and electroacoustic efficiency of the single-element and six-element electrodynamic transducers were tested respectively, and the test results were compared and analyzed.

Figure1  Photograph of the experimental system

Figure2  (a) the traditional single-vibrator electrodynamic transducer prototype and (b) the six-vibrator electrodynamic transducer prototype.

Experimental results

The transmitting current response of the multi-element electrodynamic transducer in the ultra-low frequency band is significantly improved compared with the traditional single-element structure, showing a stable gain advantage across the entire test frequency band. In terms of radiated acoustic power, the N-element transducer structure can increase the original radiated acoustic power to N² times, and the electroacoustic efficiency to N times. The overall test results are in good agreement with the theoretical calculations and finite element simulation results, fully verifying the effectiveness of the multi-element mutual radiation effect in effectively improving the acoustic radiation performance of ultra-low-frequency electrodynamic transducers by increasing the radiation resistance.

Figure3  Test results of the transmitting current responses (TCR) for the electrodynamic transducer prototypes.

Figure4  Table of theoretical comparison for performance parameters

The effectiveness of the amplifier in this experiment

Amplifying the small-signal current input from the signal source to drive the transducer.

Application fields

unmanned underwater vehicle (UUV), ultralowfrequency underwater acoustics, underwater acoustic countermeasure, ocean acoustic measurement, electrodynamic underwater transducer