The 'Scimitar' design of the prop's on the C-130 Hercules you saw, are interesting in that it's pretty much the last thing that can be done propellor-wise before you go to a Fan-jet engine. You'll also notice that the original C-130 had 4-blade prop's with large flat paddle-like blades. The one you saw would have had the NP2000 8-bladed 'scimitar' props. Propellors are matched to the horse-power of the motor they are attached to. The C-130 Hercules has had an ongoing enhancement program that has up-rated the engines as well. If you want to get more power out of an engine, you need to put a larger diameter prop on it. But when you do that, you get to a point where the tip of the propeller is starting to break the sound barrier, which not only makes it loud but also reduces its efficiency. The only practical ways to make the blade longer, but at the same time minimise the diameter of the prop, is to a) increase the number of blades on the hub, and b) curve the blades so the leading edge length exceeds the radius ...
So - although it makes it quieter, it's not because of the 'slicing' - it's because the tips of the blades don't have to go as fast as for a 'straightened' version of the same prop-set.
It's notable that the Hercules could have been upgraded to have fan-jet engines, but that would impact on its short-field take-off and landing [STOL] performance. When prop's are used, they actually provide airflow over the wing which maintains the lift of the wing even at low speeds (decreases the stall speed) - so there are big advantages in using propellers rather than jets when it comes to STOL.