Noise reduction of pile driving and unexploded ordinance detonations at offshore wind farm installation sites

Abstract

Pile driving noise during the installation of monopile foundations for offshore wind farms can produce very high noise levels, and strict regulations on this underwater noise exist around the world. In addition, the controlled detonation of unexploded ordinance (UXO) at offshore wind farm installation sites in European waters is an additional challenge and reduction of this noise is a major challenge. This paper discusses a tunable acoustic resonance-based underwater noise abatement system for use on marine pile driving, controlled UXO detonations, and other applications. The system consists of arrays of underwater air-filled resonators, which surround the noise source and are tuned to optimally attenuate noise in a frequency band of interest. System demonstrations that were conducted at two offshore wind farm sites in the North Sea will be discussed, in which peak sound pressure level reduction of nearly 40 dB was measured, and almost 20 dB sound exposure level reduction was measured. Laboratory testing on noise generated by a combustive sound source, used to simulate UXO noise, will also be discussed. The method of deploying these resonator arrays in a simple collapsible framework, operational advantages of this approach, and future projects using this technology will be shared.