GS724T fans

Sorry, not a much better question - yes, the air is moved mechanically of course. But this is just the beginning.

Almost all of these switches use axial fans. Specs vary between each hardware version. Nominal diameter, mounting hole distance, thickness, then voltage, nominal RPM, RPM regulation like voltage or PWM for example), airflow at nominal RPM, tach signal, ...

You are advised to check what is installed on your hardware. Search for the same or very similar equivalent with matching specs. 

Netgear does not offer replacement fans. You need to work with the popular sources like eBay, Amazon, ... where various vendors have offerings up. Still, the information might be wrong, so watch your step.

Last advise: A silent fan not never provide the correct cooling. Never. Even if we have some freaks around here and on other communities pushing fan makes like ebm-papst or Noctua. best stuff you can find for e little bit more $$$. Yes, these make excellent fans, Noctua makes extremely silent fans, top notch quality. The noise however depends on the fan tip speed - and so does the airflow, as well as the pressure the fan can generate. Be warned: You can easy end with silent fan. If the hardware monitoring does expect an RPM in the range of 8k...16k RPM there can be still errors shown in the hardware monitor. it's as essential to have the right engine, the matching propeller and the required take-off RPM and thrust. Otherwise your aircraft won't perform, won't come off the ground before the runway end, will poorly climb or not reach the expected horizontal speed.