Embedded very-low-frequency underwater acoustic acquisition technology and experimental study for underwater explosion monitoring

Very-low-frequency (VLF) underwater acoustic monitoring is a primary means for monitoring specialized underwater explosions. In view of the limited availability of dedicated off-the-shelf VLF underwater acoustic monitoring equipment and related technologies, this study investigates embedded VLF underwater acoustic acquisition techniques and develops an embedded acquisition device for VLF signals generated by specialized underwater explosions. The device adopts a modular architecture that separates the sensor from the controller, and integrates a low-noise transimpedance amplification and differential conditioning circuit, a high-resolution ADS1285 analog-to-digital converter, an STM32F429 control core, and an eMMC-based storage system. Multi-node time consistency is achieved through GNSS timing combined with a PPS synchronization mechanism, while cyclic recording and plug-and-play data export are implemented using the FATFS file system and USB MSC mode. In underwater explosion experiments, the device successfully recorded the initial shock-wave arrival, bubble pulsation signals, and long-range VLF underwater acoustic signals, thereby demonstrating the capability of the system for low-noise acquisition, reliable time synchronization, and long-term autonomous monitoring. The results indicate that the device can provide long-term stable acquisition and storage capabilities, meeting the engineering requirements of VLF underwater acoustic monitoring, explosion effect assessment, and underwater acoustic experiments, and offering key technical support for the development of VLF underwater acoustic monitoring equipment.