An apparatus that produces a gaseous vapor baffle that isolates an undersea sonar system from acoustic noise. The apparatus allows for craft carrying undersea sonar systems to travel at relatively high speeds while substantially isolating the undersea sonar systems from acoustic noise interference produced by propulsion systems, hull appendages, waves and bubbles. The apparatus has a support strut that has one end that is joined or attached to the hull of a craft. A sonar pod is attached to the other end of the support strut. The support strut has a ventilation duct and a plurality of ventilation ports. A cavitator is attached to the support strut and produces a sheet cavity as the craft travels in the water. Pressurized air or other gases are injected into the ventilation duct which then exit through the ventilation ports and into the sheet cavity. The pressurized air or gas exiting the ventilation ports expands the sheet cavity to form a gaseous vapor baffle that isolates the sonar pod from acoustic noise.