Real-Time Acoustic Monitoring of Offshore Wind Farms

Buoys equipped with hydrophones and acoustic recorders are used to evaluate the level of underwater noise on offshore wind farms. In recent years, the presence of certain species of marine mammal during offshore infrastructure works (pile driving, drilling, etc.) has been a major environmental concern.

By way of example, one such species is a certain porpoise endemic to the German coast that is very sensitive to sound waves; this mammal mainly uses its hearing for positioning in lieu of its very limited sight. In order to safeguard the species and its natural habitat, German legislation since 2018 has imposed a cap on sound levels caused by all offshore activities.

Offshore wind farms developers, therefore, are required to measure, monitor, and restrict noise caused by building work, and, today, underwater noise monitoring (UNM) regulations are enforced in most countries as a means of protecting aquatic life.

CALCULATION OF ACOUSTUC DESCRIPTORS IN REAL TIME

Since 2014, RTsys has been providing offshore developers with buoys equipped with acoustic recorders able to analyze data in real time. Users on offshore wind farms, whether local regulators, planning boards or construction companies, can measure real-time audio levels and carry out live monitoring when sound levels exceed regulation limits. The results are transmitted using 4G or iridium to a specific internet platform developed by RTsys. This algorithm is embedded on every RTsys underwater acoustic buoy, like REMHY and RUBHY, both used by companies like Jan de Nul, Boskalis, Ailes Marines (Iberdrola France), Gardline, Deme, and Geosea to monitor offshore piling activity.

A specific human-machine interface (HMI) has been developed to facilitate user analysis and understanding of several indicators such as SEL, SPL, 1/3 octave bands, as well as ambient noise. The HMI also allows real-time display of FFT and spectrograms. Therefore, users have a tool to manage construction work, enabling them to make quick and reliable decisions. Moreover, the real-time acoustic data interface has been developed in collaboration with end-users to provide them with an interface which better meets their needs, but which is also easy to understand for non-acoustic specialists. Thanks to this intuitive interface, offshore construction companies and regional acoustic planning boards are able to access and exchange data more freely.

WHEN INNOVATION PARTNERS REGULATION

In order to develop reliable and fit-for-purpose tools for our end-users all over the world, RTsys relies on—and adheres to—the in-country underwater acoustic recommendations and standards set by local agencies, like the German Federal Maritime and Hydrographic Agency (BSH, Bundesamt für Seeschifffahrt und Hydrographie), which authorizes offshore wind farm development projects in German waters.

Thanks to RTsys’ commitment to these standards, innovative technology developed by RTsys is now officially recognized by many authorities around the globe. In addition to calculation calibration, the methods used in acoustic buoys are transparent throughout the measurement chain, an initiative that enables measurements taken to be monitored and validated.

Ten years after the initial product testing, RTsys acoustic buoys are now deployed on offshore wind farms throughout America, Northwest Europe or Southeast Asia.

BEYOND OFFSHORE WIND

Founded in 2010, RTsys is part of the Sea Vorian Group and designs and manufactures a comprehensive range of ocean equipment and marine robotics for the defense sector (MCM and ASW), the marine science community (IFREMER, KIOST, SHOM, DSO…), and the offshore energy markets.

All RTsys equipment is equipped with an electronic board reference SDA® (Synchronous Data Acquisition), a proprietary technology that enables complete operator control of all hardware and software features. SDA® is a result of significant year-on-year investment in R&D and ultimately means that RTsys works fully independent of any third-party IP supplier.

Further R&D led RTsys to the design and supply of world-renowned AUVs and diver-held sonar systems. While RTsys continues to grow, the company now focuses on four core lines of business:

1. AUTONOMOUS UNDERWATER VEHICLES (AUVs)

RTsys’ range of AUVs includes two-men-portable units as well as ultra-compact micro AUVs. These powerful, long-endurance vehicles support a wide range of interchangeable payloads—including SSS (both 2D and 3D image data), CTD and any other water quality sensors. The integrated INS and DVL, combined with a surface communication module, enhance navigation capacities to an accuracy of less than 5 meters independent from the distance covered.

2. PASSIVE ACOUSTIC MONITORING (PAM)

RTSYS is world leader in the design and manufacture of acoustic recorders, buoys and software for both post-processing analysis (up to 180 days autonomy) and real-time assessment.

The acoustic monitoring and recording combined with multiparameter sensor logs offer the best answer to a wide community of users, from Marine Renewable Energy for noise and environmental impact assessment, to scientific users in marine biology, ambient noise and water quality monitoring.

3. MINE COUNTERMEASURES (MCM)

RTsys provides EOD Divers and Special Forces with a complete range of AUVs and diver-held navigation and sonar systems to upgrade divers’ efficiency and safety during MCM operations. The SonaDive handheld sonar is especially designed to assist military and professional divers in navigation and underwater object detection.

The contribution of native acoustic communication offers the most improved navigation thanks to the Sparse-LBL technology and allows a constant accuracy during the mission (less than 5 meters like the AUV range). Divers can communicate among themselves and with the surface unit in real-time via the acoustic modem, sharing contacts and text messages within a 2 km range, which extends to 5 km using RTsys relay beacons.

4. ANTI SUBMARINE WARFARE (ASW)

Finally, RTsys is a world leader in the design and manufacture of ASW sonar characterization and ASW target training. The SIERA system offers the most reliable solution for the characterization and calibration of underwater acoustic systems (hull-mounted sonars, dipping sonars, variable depth sonars, and buoys), while SEMA can act as an autonomous and recoverable acoustic target for ASW training. It is operable for all kinds of platforms such as surface vessels, submarines, helicopters, and ASW aircraft.

For more information, visit: rtsys.eu.

This feature originally appeared in Ocean News & Technology's Magazine April 2022 edition—Green Energy. To read more, access the magazine here.