Abstract
Since 2016, underwater noise from the construction of offshore wind in Danish waters has been addressed by guidelines from the Danish Energy Agency. These guidelines were updated in 2022 and specify technical methods for performing numerical prognosis and on-site measurements. Acoustic criteria are stated for compliance, including Permanent Threshold Shift (PTS) and behavioral impact. These criteria are based on auditory frequency-weighted levels.
Impact pile driving and vibratory pile driving installation techniques are addressed, with separate methods for modeling and measurements. Concession holder is required to carry out a prognosis to estimate the environmental impact using the given sound source and propagation properties and calculate the acoustic metrics experienced by a receptor (marine mammal) while it is fleeing away from the noise source. The prognosis must be carried out for two to three scenarios, on fully numerical or semi-empirical basis: reference case, planned construction case, and if relevant a specific case including acoustic deterrent device (ADD).
For comparison with measurements during pile installation, the prognosis is required to provide predictions for certain acoustic metrics that are suited for direct measurements.
On-site measurement of underwater sound during installation is required for two purposes: verification of the propagation model used for the prognosis and demonstration of compliance with the acoustic criteria.