It has to get that air moving at comparable speeds to be as efficient as the traditional way. The trick here is to get the air move faster with less sound. It's possible because of larger airfoils, so they can get more laminar flow and with more laminar flow comes less sound.
Right, if you were building a wing. The problem is that here we are after heat exchange and, as I understand it, the last thing you want is laminar flow due to the accompanying boundary layer.
https://en.wikipedia.org/wiki/Laminar_flow