[SOLVED] Fans/Coolers make noise when slowing down. Dangerous?

[Cametovisit]

When my PC is under load (playing a game) and then I turn it off suddenly. When the fans/coolers start slowing down, there are a couple of seconds of a noticeable revving sound. It doesn’t sound bad or dangerous to me but it clearly sounds like a fan trying to slow down and hence making noise.

I am not sure which fan/cooler causes this. I run an 11400f with stock, 3060ti gaming X and a Cooler Master H500 case with the two big fans in the front and a 120 MasterFan Halo in the back.

Should I worry about this?

 

[Lafong]

Use a hollow tube like a paper towel insert held up to your ear like a megaphone to find out what fan or fans are acting up.

Confused about "revving" sounding like "a fan trying to slow down".

Maybe you can record it?

It could be fans speeding up momentarily during shutdown as Windows gives up control.....just as fans are usually loud during the first few seconds of startup before Windows gains control......although I can't recall hearing that on my quiet system.

 

[Cametovisit]

Use a hollow tube like a paper towel insert held up to your ear like a megaphone to find out what fan or fans are acting up.

Confused about "revving" sounding like "a fan trying to slow down".

Maybe you can record it?

It could be fans speeding up momentarily during shutdown as Windows gives up control.....just as fans are usually loud during the first few seconds of startup before Windows gains control......although I can't recall hearing that on my quiet system.

I don’t think revving was the right word. Yes it’s pretty much what you said but it happens when they slow down, not when intensifying.

 

[drea.drechsler]

I don’t think revving was the right word. Yes it’s pretty much what you said but it happens when they slow down, not when intensifying.

It's probably just going through a self resonant frequency of a component in the case. That's when the speed of the fan matches a frequency of a surface or component that makes it vibrate like a guitar string. The way to fix it is change the resonant frequency of the part. You have to find it first, that entails touching things to see if the sound changes when it happens. Sometimes gently tapping on things with a soft object, like a pencil eraser, can cause it to make sound at the same frequency. Once you find it put a couple pieces of tape on it to change the frequency to something out of band. Sometimes it might be as simple as moving a wire which is resonating along it's length.

 

[Cametovisit]

It's probably just going through a self resonant frequency of a component in the case. That's when the speed of the fan matches a frequency of a surface or component that makes it vibrate like a guitar string. The way to fix it is change the resonant frequency of the part. You have to find it first, that entails touching things to see if the sound changes when it happens. Sometimes gently tapping on things with a soft object, like a pencil eraser, can cause it to make sound at the same frequency. Once you find it put a couple pieces of tape on it to change the frequency to something out of band. Sometimes it might be as simple as moving a wire which is resonating along it's length.

https://youtube.com/shorts/9IBdnI-JQes?feature=share

Here listen

 

[drea.drechsler]

https://youtube.com/shorts/9IBdnI-JQes?feature=share

Here listen

Sounds like a resonance making some chassis parts vibrate against each other. Maybe one corner of the fan is just a little bit loose, so check screws and tighten a bit. You can gently tap the case around the fan to try and find it, or touch things as it's slowing down.

FYI: i had a very similar problem and spent hours chasing it down but couldn't find it. It went away when I opened the back panel to re-route an SSD SATA cable. I don't know what I did, but it's gone.