Unlike pressure nozzles, ultrasonic nozzles do not force liquids through a small orifice using high pressure in order to produce a spray. Liquid is fed through the center of a nozzle with a relatively large orifice, without pressure, and is atomized due to ultrasonic vibrations in the nozzle.

Every ultrasonic nozzle operates at a specific resonant frequency, which dictates the median droplet size. For example, a 60 kHz nozzle produces ,a median drop size of 20 microns (when spraying water). The higher the frequency, the smaller the median drop size.