So my launch PS4 used to be really fucking loud, in a way, that I had to turn the volume of my speakers all the way up or use headphones in order to enjoy playing games. Like hair dryer loud, just a real bummer overall. Since I'm out of warranty, i decided to open the thing and see what a fresh batch of thermal paste could achieve. After following one of the guides on Youtube I got it open and decided to check out if there was any dust in the heat sink. To my surprise i discovered a big amount of dust which I carefully removed. Afterwards I reapplied the thermal paste (pea method) and put the system back together. In this process I tried another thing to make my PS4 quieter. I got the idea for this in a forum a I found through google:
http://www.overclockers.com/forums/showthread.php/758144-Arctic-Silver-5-PS4 . Basically I put a copper coin under the preassure bracket of the PS4 to apply some tension and to prevent too much space between chip and heat sink. After everything was back together I started up the main menu of Rocket League (which is known to make the PS4 go wild) and it stayed super calm! I fired up Witcher 3 and got the same results! I can hear the fan spinning when i mute my speakers but even then it's not annoying and doesn't bother me at all. To be frank I'm not sure which one the steps i described led to these results or if it's a combination of all of them but I'm just super happy that I can enjoy my PS4 again.