Helmholtz cavities make noise, of course. Figure out exactly how these cavities work, and then you can control that noise. By adding Helmholtz cavities of sorts into the base of the Multiplier, engineers increased air pressure, and ultimately these cavities began to work as silencers.
Car manufacturers are very familiar with the principles of Helmholtz cavities. They manipulate them to their advantage when quieting exhaust systems. In the case of the Multiplier, engineers basically tuned the cavities to specifically mute sounds in the range of 1,000 Hertz, which humans tend to find especially aggravating.
Their efforts (and those heaping mountains of research cash) paid off. According to Dyson, the second-generation fan is 75 percent quieter than its ancestor. And because air moves more smoothly and efficiently through the entire Multiplier, Dyson was able to scale back on the motor. They say the new motor requires 40 percent less power.
For its quietness, the Noise Abatement Society awarded the Multiplier with a Quiet Mark award. The award goes to products that clamp down on unnecessary noise pollution.
Dyson is quite literally banking on its new, quieter fan. As with the first-generation version, the new ones are pricey. The smallest desk model starts at $300.
There's no question that the Dyson Air Multiplier is a striking invention. Its sleek design and innovative technology set the blogosphere abuzz when it launched. Perhaps in the future, none of our fans will have visible blades.