Review on 🔧 UCTRONICS Raspberry Pi Rack 1U - 19-inch Rackmount Supporting 1-4 Units, Compatible with all Raspberry Pi B/B+ Models by Sean Maile

These things are great for providing lots of stable power. On the other hand, it's like a constantly loud dog whistle that works 24 hours a day, seven days a week. It uses the driver for the official POE hat (so no configuration required) but the fan is not the same. When the Pi isn't slamming and trying to overheat, it sounds like a very loud dog whistle. When it overheats, the fan runs normally and makes loud but normal fan noise. Threshold adjustment works to get the whistle moving, but there's no way to completely turn off the broken speeds, so there will always be that noise, at least partially. Time. If you use more than one you will find that they resonate but are not quite in sync. Makes it surprisingly much worse than expected.