How loud is the underwater noise from operating offshore wind turbines?

Jakob Tougaard,Peter T Madsen,Line Hermannsen

doi:10.1121/10.0002453

Jakob Tougaard, Peter T Madsen + Show 1 more

Open Access

https://doi.org/10.1121/10.0002453

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Abstract

Offshore wind turbines are increasingly abundant sources of underwater low frequency noise. This increase raises concern for the cumulative contribution of wind farms to the underwater soundscape and possible impact on marine ecosystems. Here, available measurements of underwater noise from different wind turbines during operation are reviewed to show that source levels are at least 10-20 dB lower than ship noise in the same frequency range. The most important factor explaining the measured sound pressure levels from wind turbines is distance to the turbines with smaller effects of wind speed and turbine size. A simple multi-turbine model demonstrates that cumulative noise levels could be elevated up to a few kilometres from a wind farm under very low ambient noise conditions. In contrast, the noise is well below ambient levels unless it is very close to the individual turbines in locations with high ambient noise from shipping or high wind speeds. The rapid increase in the number and size of offshore wind farms means that the cumulative contribution from the many turbines may be considerable and should be included in assessments for maritime spatial planning purposes as well and environmental impact assessments of individual projects.

Highlights

Offshore wind is an increasingly important part of the transition to green energy and with this comes concerns for possible negative impacts on the environment
A simple multi-turbine model demonstrates that cumulative noise levels could be elevated up to a few kilometres from a wind farm under very low ambient noise conditions
The noise is well below ambient levels unless it is very close to the individual turbines in locations with high ambient noise from shipping or high wind speeds

Summary

Introduction

Offshore wind is an increasingly important part of the transition to green energy and with this comes concerns for possible negative impacts on the environment. Concerns were undoubtedly spawned by the sometimes intense debate over airborne noise from land-based turbines and the effects on humans (see, for example, Freiberg et al, 2019), and this led to a number of studies to quantify the underwater noise radiated from offshore wind turbines. Most of these studies are only communicated in hard to obtain grey literature, and many are not written in English. In European waters, it is, relevant to evaluate whether the contribution from wind farms is of a magnitude that could impact the marine environment and thereby mandate monitoring and potential mitigation of the noise in fulfilment of the requirements of the European Union (EU) Marine Strategy Framework Directive (European Commission, 2008)

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