The Impact Of Bubbly Water On Airgun Signatures

The airgun signature, especially the bubble time period, is controlled by the source depth, size of the gun and firing pressure. In addition, several studies are carried out to investigate the impact of heat transfer, viscosity, surface tension or mechanical processes inside the gun on the oscillating bubble. Another aspect that could have an impact on the airgun signature and bubble time period is the presence of small air bubbles in the water which leads to a reduced density and bulk modulus. The water can be saturated with air close to the surface due to waves or due to a leaking airgun located below other sources. We conduct experiments with a small airgun inside a water tank where the source signature is recorded. The near field pressure is measured without air bubbles in the water and for three settings with an increasing amount of air bubbles. The air bubbles are generated from a tube with several holes exactly below the airgun. An increased bubble time period and primary-to-bubble ratio is observed with an increasing amount of air in the water. The amplitude of both, the main peak and bubble peaks, is reduced with an increased amount air saturation.