Bubble curtain

Bubble curtain are a measure of the technical environmental protection in the marine environment for the insulation of noise, as it arises, for example, in the construction of offshore facilities. By bubble curtain especially hörempfindliche marine mammals such as porpoises and seals should be protected from hearing damage.

Conservation

During the construction of offshore wind farms, such as offshore wind turbines, oil platforms, research platforms, among other things, foundations are driven into the seabed under a lot of noise, made ​​holes or shed foundations. Especially porpoises that have a hearing range of about 1-150 kHz and orient themselves on ultrasound, may suffer damage due to the sound waves under water. It may involve the TTS (Temporary Threshold Shift), so a temporary hearing loss due to noise exposure, or the PTS ( permanent threshold shift), a permanent hearing loss in the animals come.

Technical implementation

To create a bubble curtain, compressed air hoses are placed around the underwater site. These are connected to compressors, as they are also used in road construction, and pump compressed air into the tubes on the ocean floor. This compressed air rises in the form of a curtain of air bubbles and forms a physico- acoustical insulating barrier to the sound waves.

When building the foundations for the research platform FINO 3, about 80 km west of the island of Sylt, the Institute for Statics and Dynamics, University of Hannover accompanied the large-scale testing of a so-called "big bubble curtain " scientifically in the BMU -funded research projects sound FINO 3 the bubble curtain generated by means of a 440 m long, provided with nozzle openings plastic pipe which has been laid out on the seabed in a radius of 70 m at the site and fed with compressed air during driving. In this way it was at a distance of 910 m, a sound reduction of 12 dB ( broadband level, SEL ) or 14 dB (peak, Lpeak ) can be achieved.

In another research project, the effectiveness and practicability of a so-called "little bubble curtain " for the construction of a wind turbine in the offshore wind farm "alpha ventus " investigated. This project was also funded by the BMU under the title sound alpha ventus. In the experiment, a sound reduction of 12 dB ( broadband level, SEL ) or 14 dB ( peak level, Lpeak ) was detected in the flow direction also. Contrary to the flow direction, the effectiveness, however, was drastically reduced due to the drifting of the bubbles. Where the use of the bubble curtain but was rejected because of lack of efficacy due flows later.