Autonomous, Directional Acoustic Profiling Float for Soundscape Characterization

Year One Fieldwork Summary

From September 23-27, 2024, the team of scientists and engineers deployed their Seatrec infiniTE float with a directional acoustic sensor for its first field demonstration off the coast of Oceanside, California.

Preparing to Deploy

In preparation for this deployment, they designed and developed a mount to suspend the sensor below the float body. To accommodate for this added weight and ensure the appropriate amount of buoyancy, they introduced additional volume by extending the length of the float at the top. To capture data from the sensor, they also designed and developed a data logger and built a mount to hold the data logger and its battery pack inside the float.

Before heading out to sea, they conducted a final system integration at the Seatrec office in Vista, California. This included testing the final ballast test to ensure that the float buoyancy engine could accommodate the additional weight from the sensor and its mount, testing the communications system to ensure the satellite communications link was functional, connecting the data logger battery and external sensor connectors to the data logger, and a conducting a full test of the float with the sensor connected to make sure everything was in working order.

Testing the Float

On July 26, they successfully deployed and demonstrated the float at sea for the first time for three 8-hour-long dives down to approximately 400 meters (1,312 feet), where it remained "parked" for several hours. After surfacing and relaying its position to the ship via the satellite telemetry link, it was recovered by the team.

They collected approximately 24 hours of uninterrupted directional acoustic data throughout the float operations, including diving and parking at depth.

Most of the data represented ambient noise, but the occasional boat sound was also captured. The quantity and quality of the data collected was enough to meet the goals of this field demonstration. Thus, no further deployments were conducted.

Next Steps

This was just the first of two demonstrations planned as part of this project. It paves the way for a longer duration, deeper water test, currently scheduled for summer 2025. Until then the team will:

• Use data from this deployment to help develop onboard processing algorithms.
• Refine the float controls to incorporate data logger controls.
• Enable time synchronization between the float and the data logger.
• Refine the data logger communications to be able to request specific data segments from the data logger in order to process them for telemetry.
• Implement efficient onboard processing for telemetry.
• Develop a deepwater mission based on the energy requirements of the directional acoustic sensor and associated electronics.

This demonstration was likely the first time that directional acoustic data was collected at such depth using an autonomous profiling float. Ultimately, the team hopes this float will enable deepwater exploration of ocean soundscapes in difficult to reach regions of the global ocean.