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

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.

Underwater legged robotics: review and perspectives

“…The developers of the underwater quadruped, AquaShoko [72], tried to harness this drawback to enable a controlled descent with minimal risk of overturning by regulating the legs position, to modulate the relative position of the CoG and centre of buoyancy. Being able to regulate the underwater weight of ULRs through some sort of buoyancy control device or adapting the buoyancy engines used by gliders [73] has never been attempted before, but it would have interesting implications. Transitioning from negative to positive buoyancy would allow simple resurfacing procedures.…”

“…SILVER2 has been deployed in several field trials aiming at assessing its capabilities to promote an objective comparison with more traditional underwater vehicles. The acoustic footprint of SILVER2 was observed to be lower than the one of ROVs of similar dimensions [73], and similarly, it exhibited a higher energetic efficiency during station keeping tasks [83]. In terms of manipulation, SILVER2 has been equipped with a soft pneumatic arm to collect several objects [125] and other various end-effectors including sediment samplers and a soft tendon driven gripper.…”

“…Cabled multiparametric videoplatforms allow conveying continuous power and uninterrupted data transmission, making them among the best monitoring options for studies dedicated to ecological multidisciplinary monitoring focusing on species (including commercialised ones), communities and biodiversity changes at different temporal scales [13]. When those assets are connected to locally docked autonomous URLs, a consistent expansion of their spatial sampling capability is enabled, being this monitoring achieved at low sediment/substrate footprint (compared to crawlers) [24] and acoustic signature [73]. The feasibility and efficiency of such an expansion is a central focus for those monitoring actions (feeding new types of data to enable novel conservation actions and management policies of ecosystem services), whose efficacy should be validated by specific pilot actions [15].…”

Bioinspired robots can foster nature conservation

“…These new capabilities can eventually expand the scope of conservation efforts around the world, and introduce bioinspired robots to more hazardous and remote environments to help collect data and perform intervention tasks for conservation. Recent advancements in bioinspired locomotion utilizing animal-like propulsion methods can also enable effective monitoring and engagement with the natural environment, while mitigating issues related to noise pollution ( Picardi et al, 2020a ), and disturbance to the environment’s natural state ( Katzschmann et al, 2018 ).…”

Research Trends and Future Perspectives in Marine Biomimicking Robotics

“…The statistical approach proposed in this work is based on [ 49 , 50 , 51 ] and aimed to highlight the most promising bio-inspired robotics marine research areas, identifying temporal trends, some established and emerging research targets, and the degree of international cooperation. We focused on marine biomimetics for three main reasons: (i) ocean exploration is challenging and the exploration and monitoring require the development of innovative platforms technologies, also fulfilling the needs for space research, e.g., [ 52 , 53 ]; (ii) underwater organisms show unique adaptations to extreme conditions, which could be of inspiration for entirely novel robotic developments; and finally, (iii) marine organisms have dynamic reactions when they perceive the presence of current platforms [ 54 , 55 , 56 , 57 , 58 , 59 ] as remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs) and internet operated vehicles (IoVs) as crawlers, so that the biomimetic development will improve the exploration capability, to picture biodiversity to an extent never attained before.…”