A Minimal Metric for the Characterization of Acoustic Noise Emitted by Underwater Vehicles.

Giacomo Picardi,Augusto Sarti,Clara Borrelli,Giovanni Chimienti,Marcello Calisti

doi:10.3390/s20226644

Abstract

Underwater robots emit sound during operations which can deteriorate the quality of acoustic data recorded by on-board sensors or disturb marine fauna during in vivo observations. Notwithstanding this, there have only been a few attempts at characterizing the acoustic emissions of underwater robots in the literature, and the datasheets of commercially available devices do not report information on this topic. This work has a twofold goal. First, we identified a setup consisting of a camera directly mounted on the robot structure to acquire the acoustic data and two indicators (i.e., spectral roll-off point and noise introduced to the environment) to provide a simple and intuitive characterization of the acoustic emissions of underwater robots carrying out specific maneuvers in specific environments. Second, we performed the proposed analysis on three underwater robots belonging to the classes of remotely operated vehicles and underwater legged robots. Our results showed how the legged device produced a clearly different signature compared to remotely operated vehicles which can be an advantage in operations that require low acoustic disturbance. Finally, we argue that the proposed indicators, obtained through a standardized procedure, may be a useful addition to datasheets of existing underwater robots.

Highlights

The oceans are essential for life on Earth, hosting a remarkable and still poorly known biodiversity, representing an invaluable source of food and energy, and being involved in the balancing of the planet’s climate [1,2,3]
Based on the analysis performed and accounting for the simplicity of the recording setup, we proposed two indicators to provide an intuitive and obtainable description of the noise signature of underwater robots, i.e., the spectral roll-off point, fRO [28], and the noise introduced to the environment, NE
Data obtained in this way were not suitable for a sophisticated analysis, based on critical working assumption, they allow to provide a simple yet intuitive characterization of the noise emitted by underwater robots and perform a first order classification based on acoustic noise emitted which is lacking at the time of writing and may be of great help for operators of underwater robots who want to get an idea of the acoustic noise that they are introducing into the environment where they are experimenting

Summary

Introduction

The oceans are essential for life on Earth, hosting a remarkable and still poorly known biodiversity, representing an invaluable source of food and energy, and being involved in the balancing of the planet’s climate [1,2,3]. Thanks to the advances in marine robotics, the last decades represented a turning point for marine operations worldwide, from scientific explorations to commercial activities. The development of underwater vehicles, such as Remotely Operated Vehicles (ROVs), submersibles, and Autonomous Underwater Vehicles (AUVs) has allowed a large range of operations that were previously impossible using scuba diving techniques due to the fact of both time and depth limitations. Depending on the specific task required, different types of underwater vehicles can be currently used. AUVs are often used for long operations such as monitoring ecological parameters or mapping the seabed over wide areas. Missions are usually pre-programmed with little or no interactions with human operators except for the deployment and recovery phases. ROVs are used in missions that require the continuous supervision of an external operator, including maintenance

Methods

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Discussion

Conclusion