An ultrasound apparatus capable of mixing and/or atomizing fluids is disclosed. The apparatus includes a horn having an internal chamber, containing at least one free member, through which fluids to be atomized and/or mixed flow. Connected to the horn's proximal end, a transducer powered by a generator induces ultrasonic vibrations within the horn. Traveling down the horn from the transducer, the ultrasonic vibrations induce the release of ultrasonic energy into the fluids to be atomized and/or mixed as they travel through the internal chamber. As the ultrasonic vibrations travel through the chamber, the fluids within the chamber are agitated and/or begin to cavitate, while the free member moves about the chamber, thereby mixing the fluids. Upon reaching the front wall of the chamber, the ultrasonic vibrations echo off the front wall and pass through the fluids within the chamber a second time, further mixing the fluids.