The ultrasonic nozzle produces droplets or particles of mastered size: the higher the ultrasonic frequency, the smaller the aerosol particles (some microns). Two principles exist:
- Within the frequency range between 20 kHz and 100 kHz, the liquid is sprayed when coming into contact with a vibrating surface.
- Within the frequency range above 100 kHz, an ultrasonic emitter is placed on the bottom of a volume of liquid. The sound field produces a fountain on the liquid surface from which an aerosol is developed.