Abstract
Tidal streams provide a sustainable, green and predictable energy resource. However, devices designed to extract this energy have the potential to impact upon the natural environment through a variety of interactions. One of these interactions concerns underwater noise. The potential for environmental impact due to device related noise has not been fully understood.
Before assessing device related noise disturbance on marine life, it is essential to analyse the mechanics of ambient noise at the high energy sites where devices are likely to be deployed.
This paper focuses on a high energy flow channel subject to tidal streams of up to 4 m.s-1. Using the "drifting methodology", underwater background noise has been monitored through tidal cycles of different seasons and tides. Analysis shows that this site is subject to biologic, physical and anthropogenic noise sources that contribute differently, and for some periodically, to the overall ambient noise. A distinct increase of 30 dB re1µParms above 8 kHz during spring tide has also been observed and is investigated.
The paper shows the relationship between current velocities, the tidal height and the background noise at different times of the year. This will be useful when evaluating the impact of noise on marine life.