PoE switches dump considerably more heat than regular switches. Do you need PoE on all ports? If not, you could use a smaller PoE switch to support the PoE devices and cut down on total heat generation.

Also, the fans are often variable speed. If you can create better cooling for the whole enclosure, the fans may run at a quieter speed.

I had an interesting experience with a Ubiquiti PoE switch. I wanted to mount it under a shelf, in a cabinet. Cabling was easier if I mounted the switch upside down. The switch was a screamer and could be heard on the entire first floor. On a hunch I remounted the switch, mumbling about the difficult cable access, but the switch was much, much quieter. Depending on overall environment temperature, the fans did not run at all.

I have a customer who is a fan freak and has scattered a zillion external fans around his space, pointed at equipment. Units that typically run uncomfortably hot to touch, are now nearly room temperature.