A bubble curtain is a system that produces bubbles in a deliberate arrangement in water. It is also called pneumatic barrier. The technique is based on bubbles of air (gas) being let out under the water surface, commonly on the bottom. When the bubbles rise, they act as a barrier, a curtain, breaking the propagation of waves or the spreading of particles and other contaminants.

It can be used for the following purposes:

To reduce propagation of shock waves (e.g. acoustic waves from engines or pile driving, explosions etc ),To reduce liquid or debris floating on the surface from spreading; To prevent salt intrusion; To control the movements of fish; For decoration and airing in aquariums; A pneumatic barrier in a navigation lock.

Equipment: The technical system basically consists of a compressor and pipe or hose with nozzles. When used to reduce acoustic waves from pile driving, a distribution manifold made of plastic or rubber is commonly used.