Abstract: An acoustic device is provided comprising a reservoir adapted to contain a fluid and having an exterior surface, an acoustic radiation generator for generating acoustic radiation, and a means for delivering an acoustic coupling fluid to the exterior surface of the reservoir. The acoustic radiation generator is placed in acoustic coupling relationship via the acoustic coupling fluid to the reservoir. Acoustic radiation generated by the acoustic radiation generator is transmitted through the exterior surface and into any fluid contained in the reservoir. Uncontrolled flow of the acoustic coupling fluid at the exterior surface as a result of movement of the acoustic radiation generator is eliminated. Also provided are methods that eliminate such uncontrolled flow.