Cpu 0 fan loud sound

Hello, I have a problem with the fan from one of the processors. For 2 weeks it runs at a speed of 3640 rpm and has become noisy, the 2nd fan goes to 900 rpm and everything is ok just like the rest of the Hp z820 fans. I tried believing that everything that could be done, including from the bios, is idle. I've changed the fans between them and the speed has now moved to the other fan and the first one has returned to normal, that means mechanically they're okay. I made an upgrade to win 10 but the problem started two weeks after those. Until then there was total silence I did not hear him going, I pray long if you can help me with a solution.