The patented BeKa Shells  represent an innovative noise mitigation system based on the isolation casing principle. The system features multiple layers designed to provide shielding, reflection, and absorption of sound waves. Two hydraulically movable, acoustically decoupled half-shells are closed around the installed pile and then lowered to the seabed. Between the pile and the inner wall of the BeKa Shell, a 30 cm-wide space is filled with two-layered bubble curtains, consisting of air bubbles of varying sizes. This variation in bubble dimensions is engineered to target different frequency ranges of the noise spectrum, enhancing noise attenuation.

Flexible guide shims, made from rubber rolls, ensure the pile does not make direct contact with the BeKa Shell, facilitating continued pile penetration during anchoring. The system’s dual concentric steel isolation casings, each 20 cm thick, are separated by 15 cm of water and filled with a sound-absorbing composite material. The inner shells are further coated with 5 cm layers of sound-absorbing material to maximize noise reduction. At the lower end, sound mitigation shells penetrate the ground, decoupling sound transmission along the seismic pathway. For a 6.5-meter monopile in 30-meter water depth, a typical BeKa Shell weighs approximately 180 tons and has a diameter about 2 meters larger than the monopile itself.