A traveling wave was used to ultrasonically drive the pressurized aqueous jet of a continuous inkjet multi-nozzle type printhead, resulting in remarkable uniformity in the break-off length due to non-resonant perturbation at each jet. Acoustic behaviors of the traveling wave were studied according to the jetting conditions. Propagation of the traveling wave was confirmed by decreasing the terminator length and observing unevenness in the break-off. Measurement of the shift in the phase angle at the drop break-off points allowed estimation of the velocity of the traveling wave, which is equivalent to the velocity of sound in water. Superposition of a harmonic wave onto the driving waveform verified that the measured sound velocity was appropriate by observing periodicities in satellite conditions and break-off length along with the sound propagation. A singular point in the velocity curve, believed to be due to the presence of suspended bubbles, appeared where the drop generation was irregular. The ink was degassed and the drop generation was observed to normalize; the drop generation became irregular again with the addition of non-degassed ink.