A wave glider-based, towed hydrophone array system for autonomous, real-time, passive acoustic marine mammal monitoring

Abstract

An autonomous surface vehicle known as a wave glider, instrumented with a low-power towed hydrophone array and embedded digital signal processor, is demonstrated as a viable low-noise system for the passive acoustic monitoring of marine mammals. Other key design elements include high spatial resolution beamforming on a 32-channel towed hydrophone array, deep array deployment depth, vertical motion isolation, and bandwidth-efficient real-time acoustic data transmission. Using at-sea data collected during a simultaneous deployment of three wave glider-based acoustic detection systems near Stellwagen Bank National Marine Sanctuary in September 2019, the capability of a low-frequency towed hydrophone array to spatially reject noise and to resolve baleen whale vocalizations from anthropogenic acoustic clutter is demonstrated. In particular, mean measured array gain of 15.3 dB at the aperture design frequency results in a post-beamformer signal-to-noise ratio that significantly exceeds that of a single hydrophone. Further, it is shown that with overlapping detections on multiple collaborating systems, precise localization of vocalizing individuals is achievable at long ranges. Last, model predictions showing a 4× detection range, or 16× area coverage, advantage of a 32-channel towed array over a single hydrophone against the North Atlantic right whale upcall are presented for the continental shelf environment south of Martha's Vineyard.

A wave glider for passive acoustic monitoring of cetaceans in the Mediterranean Sea

“…More recently, autonomous observation systems (AOS) have been used for passive acoustic monitoring [5]. In particular, gliders can stay at sea for several months and are equipped with sensors to measure both environmental parameters and ambient noise [12][13][14]. Within this type of platforms, there are two main categories based on their buoyancy and locomotion system: ocean gliders and wave gliders.…”

Analysis of Electromagnetic Field Characteristics of Wave Glider

“…The authors of [12][13][14][15] developed a low noise detection system for passive acoustic monitoring of marine mammals by using a wave glider equipped with a low-power towed hydrophone array and an embedded digital signal processor. Reference [16] used a wave glider equipped with temperature and salinity depth sensors for observing surface water temperature and wave height in coastal locations with a flow velocity of approximately 0.5-1 m/s and a water depth of approximately 30-40 m.…”

Autonomous eDNA collection using an uncrewed surface vessel over a 4200‐km transect of the eastern Pacific Ocean

“…Like their UUV counterparts, USVs can be configured to meet multiple mission objectives (e.g., seafloor mapping, water column chemistry, etc). For example, USVs carrying acoustic sensors have been used for seafloor mapping (Francis & Traykovski, 2021; Gentemann et al, 2020), fish stock assessments (Dallolio et al, 2022; De Robertis et al, 2019; Komiyama, 2021; Totland & Johnsen, 2022), and marine mammal surveys (Premus et al, 2022). Given the utility and versatility of the platforms, it is somewhat surprising that greater adoption of incorporating water sampling devices on USVs has not yet occurred (Flanigan et al, 2021).…”