Distributed Sensing Collective to Capture 3D Soundscapes

Oceans are drivers of global climate; they are home to some of our most important and diverse ecosystems; and they provide a substantial amount to the world’s economy as a major source of food and employment. Sound plays a vital role in the ocean ecosystem, as many organisms rely on the acoustic environment for navigation, communication, detecting predators and finding food. Therefore, the 3D underwater soundscape, i.e., the combination of sounds present in the immersive underwater environment, is of extreme importance to ultimately understanding and protecting underwater ecosystems. Currently, the role and function of underwater sounds are poorly understood, especially in the spatio-temporal reference frame that is most relevant to ocean organisms, largely due to the lack of sensing systems that can provide the necessary spatial and temporal sampling density. This project proposes a transformative new distributed sampling system to study the underwater soundscape at revolutionary spatial (~100 meters) and temporal (~100 seconds) resolutions that is also simultaneously resolves the small-scale ocean current flow. This breakthrough is achieved by deploying a distributed collective of small hydrophone-equipped subsurface drifters, which are then localized and tracked. A technique was derived that yields the distance between a pair of devices by only listening to the ambient ocean sounds. Its power is that the position and even direction of the sound sources is irrelevant, as long as the sound field is isotropic. In addition, an incoherent beamformer was proposed to analyze the direction of dominant noise sources. At-sea deployments in the Cayman Islands in collaboration with the Grouper Moon project of Reef.org have yielded practical tests of drifter releases, showing the ability to deploy and retrieve the vehicles, as well as real soundscape data. This data was then used to analyze fish abundance by analyzing their calls.

The resources of the project are also leveraged in various outreach activities. Undergraduates were engaged through REUs as well as the PIs Engineers for Exploration (E4E) program, a highly problem-driven program that empowers students to spearhead real-world engineering challenges that impact the world of exploration and resource preservation. Relevant materials were also incorporated into COSMOS, the California State Summer School for Mathematics and Science, a four-week STEM summer program for high school students.