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26 st / March 2016 www.sea-technology.com weight are under 500 kg, which allows the RB-SDA14 to be deployed and recovered from a working boat in less than 20 min. A frst anchor makes the buoy suffciently stable and free; a second anchor was specifcally de- signed to place the hydrophone sensors in a quiet area at 2 to 3 m depth, as required by regulators. Processed Noise Information The RB-SDA14 buoy can record underwater noise and simultaneously send and display real-time noise infor- mation. It is a combination of a calibrated hydrophone ac- quisition channel and advanced processing respecting inter- national standards. It provides fexible access to information and data through Wi-Fi and VHF two-way communication. First, the VHF, covering 10-km distance, allows the op- erator to send and display real-time noise information. SEL, sound pressure level (SPL) and third-octave band levels are all calculated following ANSI and other international stan- dards that can be adapted to the local guidance. Thanks to its GPS input, the buoy coordinates and cor- rects its position from the source in order to make proper calculations. In order to be adapted to possible variations in regulations, the distance (e.g., 750 m in Germany) and the limitation threshold (e.g., 160 dB SEL) can be modifed as inputs. Calculations are made inside the buoy and transferred via VHF to be displayed on an intuitive interface in real time. It is possible to receive and display information from various computers, as well as to monitor multiple buoys si- multaneously from a single computing unit. Receiving this information in real time provides huge de- cision-making support to pile-driving operators. Indeed, by viewing the noise levels that are being recorded in real time, the operator on board the piling vessel can then adapt pil- ing strategy by increasing or decreasing the hammer energy. The Wi-Fi link, offering an approximate 700-m range, provides access to the Web interface embedded in the RB- SDA14 system. This interface can be remotely accessed at any time from any computer connected to a sister Wi-Fi an- tenna. The managing software of the RB-SDA14 interface allows for more real-time functions, such as multiple buoy access and synchronization, recording of status control and recovery of all selected .wav data. It allows the surveyors to recover the selected .wav fles and bring them back to the offce for additional data analysis and certifed report- ing. Additionally, in order to ease the reporting job, the RB- SDA14 continuously stores noise information in an Excel table together with .wav fles. Gode Wind Farm For the Gode Wind farm project, developed by DONG Energy in the German North Sea, the RB-SDA14 was de- ployed continuously for a month-long test period in spring 2015 during pile-driving construction. RTsys worked with marine ecologists and underwater noise specialists from Baker Consultants to regularly adapt the information ac- quired so that the buoy could not only be used to monitor impulse pile-driving levels but also as a decision-making tool. The surveyors also realized that the buoy and the in- terface were providing the possibility to monitor other ele- vide a complete system adapted to the feld, easy to deploy, able to monitor noise emissions in real time, and can enable the opera- tor to provide required feedback to the regulators. The second ob- jective was to propose a solution that would help operators save substantial time and money, pro- viding them with the necessary tools and information to be able to adapt both mitigation and pile- driving strategies. Development of RB-SDA14 The RB-SDA14 was designed to be deployed at a 750-m distance from each monopile. This means that the buoy has to be moved quickly from one pile to another, keeping the hydrophone at a fxed distance from the pile while monitor- ing. The area where the buoy is to be deployed, i.e., an off- shore wind farm, is very windy, with signifcant wave height. Therefore, it was important to fnd a balance between ease of deployment, fexibility of use and robustness. The RB-SDA14 is composed of a 1.10-m-diameter foat and an internal rugged tube. This internal stainless-steel tube could support up to 50-m depth of immersion. It con- tains all the electronics, rechargeable batteries, GPS and wireless communication modules. Its battery can last more than 20 days in full operation. This tube is removable and interchangeable from the foat by any operator; the concept is very close to replacing an ink cartridge from a pen. It is crucial for such application related to regulations to have the widest and most accurate calibrated listening range. The electronics of the buoy contain a fully calibrated design platform, the SDA14. Equipped with four channels, 24-bit A to D convertor of hydrophone signals, and internal storage capacity up to 2 TB, the SDA14 ensures the high- est hydrophone signal quality, with a dynamic range greater than 130 dB and a signal-to-noise ratio greater than 100 dB on the full frequency range. The removable tube allows not only quick in-the-feld re- placement, but also recording through a 24-bit A to D con- verter, with the integrity of .wav raw data stored on the in- ternal 2-TB memory. This allows the acoustic reporter to do onshore post-processing and calibration with one device, keeping the other unit ready to be deployed. The 1,800-Wh battery pack is recharged in 8 hr. The buoy deployment can take place at sea between 20 and 50 m depth and can be adapted to all types of vessels and rough weather conditions. Total mooring and the buoy (Top) The RB-SDA14 buoy recovered and tap opened for tube exchange for Gode Wind farm project. (Bottom) The interchangeable electronics and battery tube can be re- moved from the RB-SDA14 in 2 min.