We will be taking a look at both the 5400RPM and 4250RPM models of the new Gentle Typhoons.
The Gentle Typhoon is the most robust fan I've handled. The bezel is thick, heavy, and very sturdy. The blades are equally well made, and the added mass should also help reduce vibration. Another change to note about the new Gentle Typhoons is that they have a ring about a half inch inside of the bezel. This also adds stability and rigidity to the blades, and places more mass towards the outer portion of the fan, which gives it greater inertia which makes them more efficient and easy to keep spinning and provides the stability necessary to operate at high RPMs. The finish is a very flat black color, not very smooth or shiny, just flat black. It has both a 4-pin molex and a 3-pin fan cable as power options.
Here you can see the motor, which is built as well as the rest of the fan, it has no noticeable give in the horizontal direction whatsoever, which is a great early indication that it will not vibrate much. Also, giving the fan a "spin test" by giving it a sharp push, it spins freely as well as any fan I've tried, at least on par with Noctua's NH-P14 or NH-P12 fans. This is then an early indication that it have a very good bearing system, which also leads to minimal vibration, and subsequently long lifetimes.
These two pictures give you a good idea of the fan shape, and there are a few notable features about these fans that make them so quiet while still moving so much air.
Most of the noise from fans, or any other device that pushes air for that matter (airplanes/helicopters) is produced from air that swirls violently after separating from the blade, so the first thing you need to do to create a quieter air-moving device is to control the air as it leaves the blade and try to make it as smooth as possible. THIS LINK provides a real-world example of what I mean by this. The blade design is very deliberate, it's more like a "scoop" than an angled plate, which leads to less swirling of the air and accelerates the air more uniformly, minimizing noise. Another important feature of the Gentle Typhoon is the outer ring, this keeps air from rushing to the outside of the blade, "blocking" the air from swirling between the blades. The fan blades are also as close to the bezel as any fan I've seen, which once again prevents air bleeding over the edges and causing the air to swirl off the end of the blades, which is also a substantial sound source.