This has been happening for about 2 weeks... maybe its been happening longer but I've just noticed it a couple weeks ago. Every once and a while my pc fans would sound like they are revving their engines. They become louder and a different pitch mostly a higher pitch. This would happen for a couple seconds then they would go back to normal. This happens while ideling and im not sure about while under load. I can't tell which fans are making this noise or if it is my cpu cooler or my graphics card. This " revving" would happen every minute to 30 sec. or so. Sometimes right after each other.
1) check if its the PSU fan. This is not a good sign and happens more often than we would like.
2) if it's not the PSU hone in on each fan and figure out which one it is. Just replace that one fan once you find it.