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Underwater gliders are autonomous vehicles that use small changes in their buoyancy in conjunction with wings to convert vertical motion to horizontal, and thereby propel themselves forward, with very low power consumption, through the ocean for a long period of time. Gliders typically make measurements such as temperature, conductivity (to calcula...
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... many whistles were detected in the data. An example of the output from the short tonal detector is shown in Figure 7. The buzz in the same figure was not detected as it was outside of the configured detection range. ...
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... avoid these detections, the lower frequency limit of the detector can be increased. In that case some sensitivity to dolphin whistles will be lost as displayed in Figure 7. This paper has described the first attempt by NURC and the Technical University of Catalonia (UPC) to develop within an underwater glider a real-time detection/classification capability of acoustic events. ...
Citations
... However, it may affect the received sound levels for frequencies below 20 Hz. Additionally, gliders generate noise during maneuvers, which can interfere with the measurements of underwater noise (Dassatti et al., 2011). ...
Underwater noise emissions from marine vehicles contribute to increasing ocean ambient noise levels, which is a threat to marine ecosystems. Passive acoustic monitoring, normally performed using moored-anchored systems, is commonly used to assess ocean soundscapes, vessel noise, and the presence of marine species. A systematic literature review was conducted to explore the use of autonomous underwater gliders (AUG) as an alternative to traditional moored systems for monitoring and assessing ship noise levels. We conducted thorough searches in Scopus and Web of Science, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We considered 13 articles on ocean glider applications for passive surveys and 8 articles on challenges in assessing underwater ship noise levels. Our findings were supplemented with international standards and guidelines from classification societies. Gliders are effective platforms for ship noise signature assessment due to their low noise signature and extended autonomy. In addition, AUGs can perform a 3D scan of the water column salinity, temperature, and density, which are needed to estimate sound propagation loss accurately. Further research is required to assess the potential of AUGs for accurately estimating ship noise levels by integrating oceanographic and acoustic data.
... Ref. [4] described a distributed system for real-time environmental monitoring. Other methods used to measure acoustic signals are moving platforms, such as moored autonomous recorders, underwater gliders [5,6], etc. Although the systems mentioned above easily acquire underwater acoustic signals, they have some shortcomings, for example, the size is quite big, the power consumption is high, the function is unitary, and the parameters are not configurable. ...
... In the CE-DFE receiver, the channel is estimated via training sequences or symbols after the decision, and the algorithm for channel estimation is the least square. The filter coefficients are obtained by (5) and (6). In order to avoid error propagation, the training symbols are periodically inserted in the transmitted signals, and low-density parity-check (LDPC) coding with a rate of 3/4 is utilized. ...
In recent years, underwater acoustic applications have attracted much attention, for example, for underwater environmental monitoring, underwater exploration, etc. Hydrophones play a particularly important role. Although hydrophone design has been in multifarious application forms, it still needs to consider increasing demand for low-cost, low-consumption, and multiple-function devices, as well as issues around miniaturization, lossless data collection, etc. In this paper, we design a compact underwater acoustic device that has the capability of underwater acoustic signal storage, underwater acoustic signal transmission via the Internet, and decoding based on the direct sequences spread spectrum (DSSS). The key problem is how to implement multiple functions in only one micro-controller unit (MCU). The hardware and software of the proposed multi-function hydrophone are described in detail. In particular, the MCU, the pre-amplifier with gain control, and the analog-to-digital integrated chip are introduced. Moreover, underwater acoustic data storage, underwater acoustic transmission, and the DSSS receiver are depicted in terms of software. The different functions of the hydrophone are verified in sea trial experiments. The results show that the proposed multi-function hydrophone is able to sample underwater acoustic data at high quality. In addition, to demonstrate configurable parameters, the DSSS receiver with different carrier frequencies is provided. The proposed multi-function hydrophone realizes zero bit error rate (BER) when carrier frequency fc=9 kHz, and the BER with 10−3 order of magnitude when carrier frequency fc=15.5 kHz. The results show that the proposed multi-function hydrophone has great potential to explore the ocean.
... Previous attempts to capture the spatial variation of soundscapes have been through the deployment of fixed hydrophone arrays [16], drifting buoys equipped with hydrophones that passively drift across a region of interest [17], or hydrophone-equipped gliders [18], [19], [20]. However, these approaches are limited in their effectiveness in capturing spatial variation. ...
The current approach to exploring and monitoring complex underwater ecosystems, such as coral reefs, is to conduct surveys using diver-held or static cameras, or deploying sensor buoys. These approaches often fail to capture the full variation and complexity of interactions between different reef organisms and their habitat. The CUREE platform presented in this paper provides a unique set of capabilities in the form of robot behaviors and perception algorithms to enable scientists to explore different aspects of an ecosystem. Examples of these capabilities include low-altitude visual surveys, soundscape surveys, habitat characterization, and animal following. We demonstrate these capabilities by describing two field deployments on coral reefs in the US Virgin Islands. In the first deployment, we show that CUREE can identify the preferred habitat type of snapping shrimp in a reef through a combination of a visual survey, habitat characterization, and a soundscape survey. In the second deployment, we demonstrate CUREE's ability to follow arbitrary animals by separately following a barracuda and stingray for several minutes each in midwater and benthic environments, respectively.
... The tasks of underwater gliders have been performed in fisheries, environment monitoring, and other scientific and defence purposes [1][2][3][4]. Applications of underwater gliders have been conducted in large fisheries using acoustic sensors such as hydrophones for detecting and tracking objects [5,6]; others use hydrophones for tracking mammals [7,8] and vessels [9,10]. In other applications, underwater gliders have helped the researcher to get information on environment monitoring [5,[11][12][13]. ...
... Applications of underwater gliders have been conducted in large fisheries using acoustic sensors such as hydrophones for detecting and tracking objects [5,6]; others use hydrophones for tracking mammals [7,8] and vessels [9,10]. In other applications, underwater gliders have helped the researcher to get information on environment monitoring [5,[11][12][13]. Moreover, an application of underwater gliders for monitoring and surveillance is reported in [14]. ...
The main goal of this paper was to design and construct a hybrid autonomous underwater glider (HAUG) with a torpedo shape, a size of 230 cm in length and 24 cm in diameter. The control, navigation, and guidance system were executed simultaneously using a Udoo X86 minicomputer as the main server and three BeagleBone Black single-board computers as the clients. The simulations showed a controlled horizontal speed of 0.5 m/s in AUV mode and 0.39 to 0.51 m/s in glide mode with a pitch angle between 14.13∘ and 26.89∘. In addition, the field experiments under limited space showed the proposed HAUG had comparable results with the simulation, with a horizontal speed in AUV mode of 1 m/s and in glide mode of around 0.2 m/s. Moreover, the energy consumption with an assumption of three cycles of gliding motion per hour was 51.63 watts/h, which enabled the HAUG to perform a mission for 44.74 h. The proposed HAUG was designed to hold pressure up to 200 m under water and to perform underwater applications such as search and rescue, mapping, surveillance, monitoring, and maintenance.
... The payload installed on these vehicles makes it feasible to analyze the state of the marine environment and obtain operational information on weather conditions in the sailing area [2,7,8]. Moreover, underwater gliders are used in the Arctic zone [9,10], in extreme environments, which allows obtaining data on ice, oceanographic data on the presence of impurities as a result of melting glaciers, eddy formation processes [11,12], geological exploration [13,14], passive acoustic monitoring [15,16], including marine mammals movement surveillance [17][18][19][20], etc. Apart from that, it is possible to highlight an area of group application of underwater gliders. There are a number of successful studies in which groups of the SLOCUM-type underwater gliders were used [21][22][23][24]. ...
Glider-type autonomous underwater vehicles are today one of the most promising areas of marine robotics. This is confirmed by the frequent and remarkable results of various research missions and projects. The cumulative group application of underwater and no less innovative wave gliders can significantly reduce the time of obtaining oceanographic data. Together with wave gliders, one group of such robotic objects can significantly increase the efficiency, time and volume of obtaining oceanographic data. There is big interest in increasing the functionality of such a group. This article presents one of the possible alternatives to increase the functionality of a group of underwater and waveguide hang gliders. We present the process of upgrading the existing design, control algorithms and software of the SHADOW underwater glider, which was developed by the teams of the St. Petersburg State Marine Technical University (SMTU) and Okeanos JSC in order to jointly study the monitoring of underwater potentially dangerous objects with the St. Petersburg State Fire Service EMERCOM of Russia. A structural-functional approach to the group application of underwater and waveguides is also proposed, which is capable of providing oceanographic, meteorological and environmental monitoring data online, based on the developed multilayer system for planning the trajectories of group movement of objects. The results of full-scale sea trials and the developed algorithms are demonstrated.
... Underwater gliders have also been used to sense the underwater soundscape [13], [14]. Although underwater gliders have intermittent communication link to shore stations during surface time, their satellite communications have very limited bandwidth, not suitable for raw acoustic data transmission. ...
Underwater sound in the oceans has been significantly rising in the past decades due to an increase in human activities, adversely affecting the marine environment. In order to assess and limit the impact of underwater noise, the European Commission’s Marine Strategy Framework Directive (MSFD) included the long-term monitoring of low-frequency underwater sound as a relevant indicator to achieve a good environmental status. There is a wide range of commercial hydrophones and observing platforms able to perform such measurements. However, heterogeneity and lack of standardization in both hydrophones and observing platforms makes the integration and data management tasks time-consuming and error-prone. Moreover, their power and communications constraints need to be addressed to make them suitable for long-term ocean sound monitoring. Measured underwater sound levels are challenging to compare because different measurement methodologies are used, leading to a risk of misunderstandings and data misinterpretation. Furthermore, the exact methodology applied is not always public or accessible, significantly reducing ocean sound data re-usability. Within this work, a universal architecture for ocean sound measurement is presented, addressing hydrophone integration, real-time in situ processing and data management challenges. Emphasis is placed on generic and re-usable components, so it can be seamlessly replicated and deployed in new scenarios regardless of the underlying hardware and software constraints (hydrophone model, observing platform, operating system, etc.). Within the proposed architecture, a generic implementation of an underwater sound algorithm based on underwater noise measurement best practices is provided. Standardized and coherent metadata with emphasis on strong semantics is discussed, providing the building blocks for FAIR (Findable, Accessible, Interoperable, Reusable) ocean sound data management.
... Acoustic underwater gliders also have been used to detect human activity by sampling an underwater acoustic environment in the temporal domain [9] and to detect the calls of whales [15]. These two studies did not consider the glider noise, but the marine mammal detector was affected by glider noise when the short tonal sound produced by the glider's engines was similar to the signals [11], [16]. We therefore need to understand the self-noise characteristics of underwater gliders if we are to improve our use and control of these vehicles. ...
Using underwater gliders to measure underwater acoustic signals is a new measurement method emerging with the development of platform technology. Although underwater gliders are relatively quiet due to the absence of propellers, vehicle noise generated during motion is still inevitable, which will affect the recorded acoustic data. In this paper, we analyze the self-noise characteristics of underwater gliders based on simulated data by CFD technology for the hydrodynamic flow noise and experimental data acquired in an anechoic-water-tank experiment for the mechanical noise. The mechanical noise covers noises generated by buoyancy regulating (increasing and reducing), pitch regulating, rudder regulating and CTD pump working. According to the analysis results, the flow noise and CTD pump working noise could be ignored for the experimental data processing of sea trials. An experiment was conducted with an acoustic Sea-Wing underwater glider in the South China Sea from July 31 to September 4, 2018. Two kinds of noisy data were recorded, including target signals and ambient noise. All the target signals could be recognized after convolution filtering, except during the buoyancy regulating periods due to the high noise spectrum level. For the recorded ambient noise, in addition to the buoyancy regulating noise, the rudder and pitch regulating noises affected the recorded data. Then based on the acquired knowledge, a joint convolution filtering and thresholding method is proposed to remove the rudder and pitch noises from recorded noisy data. Kernels extracted from data acquired in the anechoic-water-tank experiment are used in the convolution filtering to localize each regulating action and energy thresholding is adopted to determine the duration of each regulation. All the rudder and pitch noises are removed from the recorded noisy data.
... A few types of gliders, including Seagliders, Slocum gliders and Wave Gliders, have been used in the GOM. Dassatti et al. (2011) reported mean sound levels of 109 dB, with noise peaks (approximately 125 dB re 1µPa) in conjunction with the glider at the surface, due to splashing water or the hydrophone bouncing on the surface, and during engine operation. ...
Available and relevant literature and data on previous and ongoing passive acoustic monitoring in the Gulf of Mexico (GOM) were compiled. This information was reviewed to characterize potential sound sources and their distribution in the GOM and to identify existing methodologies for acoustic source detection, localization, tracking, and classification. Acoustic sources encompass weather events, industrial and military activities (including the use of explosives), shipping, animal vocalizations, and geologic events. This review was conducted under the Bureau of Ocean Energy Management’s (BOEM) Passive Acoustic Monitoring (PAM) Program for the Northern GOM. The primary objective of the program is to design and implement a multi-year acoustic data collection and monitoring plan for both the acoustic and the biotic environments in the GOM further defining the associated baseline soundscapes. The objective of this literature synthesis was to collect and review published literature and available datasets of previous and ongoing PAM projects in the GOM for the following purposes: 1. Characterize potential sound sources in the GOM. 2. Summarize the state of current knowledge on GOM baseline acoustic noise levels. 3. Investigate existing methodologies for acoustic source detection, localization, tracking, and classification of marine mammals. 4. Identify by spatial mapping previous and current study areas. 5. Identify the most appropriate field methodologies and protocols for measuring the acoustic environment in the GOM.
... Due to the advantages in terms of self-noise and duration, as well as the flexibility for acoustic payload installation [5,6], gliders are considered to have great potential in ocean acoustics applications, for example, studying whales [7,8] and fish sounds [9], acoustic sources detection and tracking [10][11][12], and measuring the marine soundscape [13]. In [8], a real-time passive acoustic monitoring device was developed and installed in the glider, which detected and classified 14 types of calls from four species of baleen whales. ...
Underwater gliders travel through the ocean by buoyancy control, which makes their motion silent and involves low energy consumption. Due to those advantages, numerous studies on underwater acoustics have been carried out using gliders and different acoustic payloads have been developed. This paper aims to illustrate the use of gliders in underwater acoustic observation and target detection through experimental data from two sea trials. Firstly, the self-noise of the glider is analyzed to illustrate its feasibility as an underwater acoustic sensing platform. Then, the ambient noises collected by the glider from different depths are presented. By estimating the transmission loss, the signal receiving ability of the glider is assessed, and a simulation of target detection probability is performed to show the advantages of the glider over other underwater vehicles. Moreover, an adaptive line enhancement is presented to further reduce the influence of self-noise. Meanwhile, two hydrophones are mounted at both ends of the glider to form a simple array with a large aperture and low energy consumption. Thus, the target azimuth estimation is verified using broadband signals, and a simple scheme to distinguish the true angle from the port‒starboard ambiguity is presented. The results indicate that the glider does have advantages in long-term and large-scale underwater passive sensing.
... In the past years, acoustic payloads for gliders have been developed at NATO STO CMRE (former NURC) in order to detect and classify marine mammals [12]. ...
In order to improve persistence and acoustic capabilities of a Slocum underwater glider, the wings have been re-designed and a linear array of eight elements has been placed along their leading edges.
In this configuration the lift/drag ratio has increased by about 15-20% with an angle of attack (AoA) of 4° with respect to the original wing configuration.
The best directivity performances have been obtained for a sound signals frequency around 2 kHz. According to the literature review, this may be useful for cetaceans passive acoustic monitoring (PAM).
