Review on Noctua NF-A4x20 5V PWM, High-Quality Silent Fan, 4-Pin, 5V Version (40x20mm, Brown) by Jay Elgouhari

When I'm not running something intense, the PWM fan is usually off. Then, as the Jetson Nano heats up, the fan turns on just long enough to cool it down. I never notice this fan - I have to look at the blades to see if it's spinning because it's so quiet. The stock fan I replaced came with a third party acrylic Jetson Nano case, it wasn't PWM, it always ran at full speed and was a noisy little fan. I've seen other comments on the standard fan saying it's not very loud. My guess is that the low quality standard fan varies in noise from device to device. If you need silence - get Noctua PWM! I got a big one, so I had to look for longer screws. I had to get a thin one that I expect will work well and use existing hardware. Either way, if peace and sanity are worth a few cups of coffee to you, get a Noctua PWM fan, such an improvement over the stock fan that came with the third-party Jetson Nano case.