It's quiet enough, I guess. I always play with headphones, and I don't use very high volumes (can't measure exactly on console, but I use it at 24/100 on PC), but the noise hasn't been an issue with that setup with the only exception being God of War 2018's map screen, that thing gets LOUD. I play on a PS4 Pro
Though I suppose I don't necessarily play the most demanding games out there, since I play most of my stuff on PC. I prefer the performance mode in Horizon just so it won't drop in towns, so my console is less stressed out in general. Most of my time gaming on the PS4 is spent with Bloodborne, Kingdom Hearts II and the Uncharted Collection. Two games that were already 60fps on the base PS4 and one that doesn't have a Pro patch anyway. Also played a ton of Yakuza 0 last year, another 60fps on base PS4 game.
I can hear my PC when I'm playing close to it, and it's still not loud enough to bother me, so the PS4 is definitely quieter than that.
Either I got lucky or it's really more about the games I play. I did play quite a bit of Uncharted: The Lost Legacy and plan on playing more times, so I'll try to notice if that one gets loud.