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Full text: Monitoring and Assessment in Regard of Technical Sound Mitigation Developments - a Perspective from MarinEARS

DAGA 2020 Hannover 
Conclusion from pile driving noise and 
abatement system application during German 
OWF constructions 
From 2013 onwards pile installations in the German EEZ 
took place at two to five OWF*‘s per year on average. Due to 
Ihe increase in megawatt capacity of wind turbines, which 
approximately doubled within this period, the number of 
wind turbines per windfarm, and hereby the number of pile 
driving events decreased. However, pile diameter have 
reached values of up to 8 meters at the pile basis. Despite 
increasing pile diameters and water depths of up to 40 
meters, a compliance with the mandatory threshold could 
has been achieved reliably since 2014. 
The effectiveness of technical noise abatement systems 
applied is evaluated according to standards given by [4] and 
[5]. Efforts by the industry have significantly advanced 
technical noise mitigation systems in the past years. In the 
last eight years, three basic noise abatement systems have 
been applied successfully in German waters under real 
offshore conditions: 
Big Bubble Curtain systems (BBC), far field noise 
abatement at distances >= 60 m around the piling 
location, 
isolating casing systems from IHC noise mitigation 
screen (NMS) at near field with multiple functions 
fsuch as holding and positioning the piles and 
allowing for controlling verticality) and 
Hydro Sound Damper (HSD) at near field around 
the pile, mostly operated from the pile gripper 
system. 
Data from the monitoring of these three noise abatement 
systems in the German EEZ of the North and Baltic Sea 
available in MarinEARS have been analyzed in the 
framework of a R&D project funded by the Federal Ministry 
of the Environment and Nuclear Safety (BMU). The results 
including current knowledge and field experiences are 
published in the final report of the project [61 
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a 40 
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non-mitigated ” 
”  mitigated (HSD+DBBC} * 
“a U Lean ra 4 ml 
100 1000 10000 
Central Frequency (Hz) 
Figure 4: Example of an analysis with MarinEARS: 
comparison of the SELos measured for pile driving events in the 
German EEZ with and without the application of technical sound 
abatement systems. 
Figure 4 shows an analysis from MarinEARS regarding the 
comparison of the SELos obtained for a pile driving event 
with and without the application of technical sound 
abatement systems. In addition to a temporal signature of a 
sound source. its spectral characteristic 1s a very important 
factor for the assessment of noise for marine life. Technical 
noise mitigation systems (singular or combined) are efficient 
as they are able to reduce the broadband SEL value by more 
than 20 dB. The noise reduction is however frequency 
dependent. Bubble curtain systems may provide an 
especially efficient mitigation of high frequency components 
of the piling noise, which is relevant for e.g. harbour 
porpoises. 
Lessons learnt and Outlook 
The noise generated by pile-driving can be significantly 
reduced by technical noise abatement systems. Level 
reductions (insertion loss) of up to 24 dB can be achieved 
compared to unmitigated pile-driving under the premise that 
technical sound mitigation concepts are applied successfully. 
Three different noise abatement systems were applied during 
the majority of the OWF construction in the German EEZ 
under real offshore conditions during the previous years. To 
date, technical developments regarding noise abatement 
systems by the industry have led to a reliable compliance 
with the threshold since 2014, despite increasing pile 
diameters and water depths at project sites. Cross-project 
evaluations regarding noise emissions and the application of 
technical solutions are facilitated by the comprehensive data 
basis of MarinEARS and provide a valuable knowledge base 
for future OWP projects. 
Literature 
[1] Lucke K., Lepper P.A., Blanchet M.A. & Siebert U.: 
Temporary shift in masked hearing thresholds in a 
harbor porpoise (Phocoena phocoena) after exposure to 
seismic airgun stimuli. Journal of the Acoustical 
Society of America 125(6) (2009): 4060-4070 
BSH Offshore wind farms: Measuring instruction for 
underwater sound monitoring. Current approach with 
annotations , Application instructions (2011). 
ISO 18406:2017-04: Underwater acoustics — 
Measurement of radiated underwater sound from 
percussive pile driving (2017). 
DIN SPEC 45653:2017-04, Offshore wind farms - In- 
situ determination of the insertion loss of control 
measures underwater (2017). 
BSH Offshore wind farms: Measuring Specification for 
the Quantitative Determination of the Effectiveness of 
Noise Control Systems. Current approach with 
annotations. Application instructions processed by 
Müller A. & Zerbs, C. (2013). 
Bellmann, M., Brinkmann, J., May, A., Wendt, T., 
Gerlach, S., & Remmers, P.: Underwater noise during 
impact pile-driving: Factors influencing impulsive noise 
and technical options for complying with thresholds at 
activity level. Lessons learned report on the application 
of noise abatement systems. Technical Report (2020), 
R&D project UM16 881500 funded by the German 
Federal Ministry of the Environment on behalf of the 
Federal Maritime and Hydrographic Agency (BSH). 
[2] 
[6] 
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