This is also true for radiator fans that have a wide speed range of 200-2000RPM and can result in an ultra-quiet operation when the CPU is not under 100% load. The increased speed range of the fan ...

Air coolers are plenty capable next to the best liquid coolers, but importantly they're also quiet and affordable. Take that, liquid cooling. The best CPU air cooler right now is the Noctua NH-D15 G2.