For the first time in five years, Dyson has redesigned its popular (and pricey) Air Multiplier, an unusual fan that replaces blades with a ring of smooth-flowing air. After three years testing and spending £40 million, the company came up with the line of Dyson Cool fans released today. The new design doesn't look that different from the previous models at all — but that's because all of the redesign happened below the surface. Watch the video below to see how engineers at Dyson restructured airflows, created Helmholtz cavities — special chambers designed to reduce noise — and overhauled the entire inside of the base to make a fan that they claim you'll only see, and never hear.