A line is run through the variable capacitor (right) and then to the Piezo-Ceramic Transducers (PZT), which are the solid state speakers attached to either side of the flask (center). These PZTs create the resonant sound waves which will trap a bubble at the center of the flask. The key to this resonance is the alignment of the acoustical phase of the flask and the electrical phase of the variable capacitor. Other lines lead to the oscilloscopes so the frequencies can be monitored and adjusted precisely.