The present study focused on the effervescent atomization of oil-in-water emulsions with a special look at the unsteadiness occurring in the internal mixing pneumatic atomizer at certain process conditions. Spray drop size measurements were conducted using a laser diffraction spectrometer at a data acquisition rate of 250 Hz to analyze changes over time. Different characteristic values for the spray morphology and behavior were studied for their suitability to describe timely changes and their effect on spray results. It was found that the flow pattern inside the mixing chamber of the atomizer not only influences the averaged spray drop size but also its temporal fluctuation. Oil drops of atomized emulsions broke up at all investigated ALR, however, no measurable influence of spray unsteadiness was found with the chosen nozzle design. (c) 2016 Elsevier B.V. All rights reserved.