Ultrasonic humidifier work by vibrating a small disk at incredibly high frequencies to break up water into extremely small droplets, which evaporate soon after they leave the humidifier and humidify the air. There are two main ways these might work: by either vibrating the transducer underwater and blowing out the produced fog, or using a special transducer which has small perforations in it, pulling water up from the water reservoir through a cotton rod by using capillary action.
