Big Bubble Curtain – HY75
The Big Bubble Curtain (BBC), or in German ‘Großer Blasenschleier’ (GBS), is a compressed air system for sound absorption in water. We have developed this system in line with respective conditions and with subsidies from the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear safety (BMUB). The system serves primarily to provide sound protection during offshore pile driving and offshore munitions blasting. The Big Bubble Curtain especially protects porpoises and seals which use ultrasound as orientation in water. The limit specified by the BMUB of 160 dB sound exposure level (SEL) applies in German waters of the North and Baltic Sea, measured at a distance of 750 m from the sound source.
How it functions
We apply a flexible tube system fitted with special nozzle openings. It is installed at sufficient distance on the seabed around the location where sound is generated. Up to two rings can be applied depending on the condition of the seabed and the water current. A ship fitted with special compressors presses up to 10 bar of air into the tube system during sound generation. The compressed air is discharged via the nozzles provided. The bubble curtain develops as a result of the continuously rising air bubbles. It changes the physical condition of the water. Acoustic waves are repeatedly broken and the noise level is reduced by up to 95 %.
The tube system can be salvaged after each use. It is independent of all other working units and does not leave any trace in the seabed.
The maximum sound absorption achieved up to now is 15 dB with one tube ring, and 18 dB with two tube rings. Installation and deployment of the Big Bubble Curtain are variously dependent on wind force, wave height, water depth, and the current environment conditions at the respective construction site.
History and Development
The Big Bubble Curtain originates from the compressed air barrier technology which we have been using for more than 50 years to protect floating debris and oil. On the initiative of the NABU Schleswig-Holstein and various environment protection associations, in 2006 we initially tested whether the system of a compressed air barrier could also be used to minimize underwater noise. Munitions from the Second World War were to be blasted in the Kiel Fjord. A nature reserve for porpoises nearby was in acute danger.
The system was first used in 2008 in the offshore section of the Baltic Sea during pile driving to build the Research Platform FINO3. The BMUB made a considerable contribution to cover costs for scientific research and further development. The University of Hannover and the company, BioConsult, itap GmbH were also involved in the project.
The Big Bubble Curtain is now used in almost all construction work for offshore wind farms and blasting work in the North Sea and Baltic Sea.
- Independent work cycles
- 60 minutes for 160 m hose-ring
- 45 minutes for 75 m hose-ring
- Specialized ship
- Polyethylene compressed-air pipe
- Special nozzles
- Air-supply, nozzle and drainage hoses
- Control valves
- Drainage valves
- alpha ventus
- Amrumbank West
- Baltic 2
- Borkum West II
- Borkum Riffgrund
- GLOBAL TECH I
- Nordsee Ost