Ultrasonic cleaning is a very effective cleaning technique. The cleaning effect in an ultrasonic bath is caused by sound waves (which are not perceptible to humans) being sent through the water with the cleaning fluid. As a result, tens of thousands of air bubbles are generated and they burst together by the sound waves.
These implosions result in a multitude of small flows through the cleaning liquid, the currents function like a brush and soak the dirt away from the objects, resulting in ultrasonic cleaning. This happens without scratching or sanding and places are reached which you cannot reach with manual cleaning.