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New CPU cooling, why do fans make buzzing noise? is it normal?

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Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
I just put in a megahalem onto my system and put 2 s-flex SFF21F fans onto it, they are 28db fans but they both make this odd buzzing noise.

Is this buzzing noise (kind of like a bee flying near you) normal? I know its comming from my fans cause when i put my ear near it, i move to the next fan and the buzzing fades and returns so that means both fans are making it.

I don't know what could be causing this, I changed the speed of the fans in bios and rebooted, and still the same buzzing noise even tho the fans went from 100% to 50%.

What could it be? Is it the fan clips? did I install it wrong?
 
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Zonnza

Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
Here's something I just noticed while experimenting with it. When I take my hand and cover the top fan while it is operating (blocking air flow), the noise goes away.

I have the megahalem facing upwards so airflow goes up. With a pushpull config with both fans, the air is pushed up. My case has 1 200mm fan on top and 2 120mm fans on the back just for reference. I'm trying to figure out what it could be at this point.

It may be the 2 fans on the cooler themselves? Or maybe the airflow in the case?


UPDATE: I downloaded speedfan and took a look at the the rpm of my fans, both are at 100% but the bottom fan pushing air is moving between 1450-1500rpm while the top fan pulling air is 1500-1550rpm. Could this be an issue?
UPDATE2: I took a packaging box of one of the fans and put it on top of the top fan to simulate my hand over the fan. The noise went away like it did with my hand but the rpm of the top fan went to <1450 and the bottom fan is 1450 and sometimes goes up a tiny bit.
 
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Zonnza

Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
Another update:

I took the top fan off the cooler, noise stoped. I then took it and made it so its PUSH-PUSH config and no noise... If i lay the fan ontop of the cpu cooler then the noise continues. I don't know what to do to solve this, I want to run 2 fans on the cooler but I don't know how to set it up so it doesnt kill it.


Maybe orienting the cooler to be pushing air to the left instead of up be better?

Would it be an issue to do a push-push config? lol
 

Conumdrum

Member
Joined
Sep 15, 2007
Location
Small town Emlenton, PA
You probably got one HS fin thats touching the fan case ever so slightly. Try finding a way to isolate the fan from the HS side. Teeny bits of rubber or something. It's for sure a vibration issue methinks.
 

WayOut

Member
Joined
Nov 21, 2009
Location
Seattle, WA
Happens sometimes on my A+ Diablo case; the big side fan has a little wire through it that is occasionally caught onto the fan and makes a buzz. Best guess is that the fan's hitting something, either a wire, cable, part of the case, or some other erroneous object. My guess is that why it stops when your hand's over it is that it's no longer sucking the wire/object into the fan's reach when you stop the airflow. Good luck :)
 
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Zonnza

Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
I can raise the fan a few mm's off the top of my HS and it wil lstill make the noise, even tho it is NOT touching it... I got a feeling it has to do with airflow

Still looking around and nothing, i tryed putting the case on its side to see if it was because of the orientation, and nothing

So im still at a loss. I think this noise isnt normal so I need to figure it out.
 

Conumdrum

Member
Joined
Sep 15, 2007
Location
Small town Emlenton, PA
Are they PWM fans? I don't know a lot about those fans. Are they connected to the PSU or something else? Some PWM fans make noises, not all, some if a bit faulty.

Just rambling, try off the PSU if using the mobo or a fan controller.
 
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Zonnza

Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
They are connected to the mobo, but they do have converters to connect to molex power cords, i tyed both ways and still same issue... im going to assume it is because of the airflow making the noise...

one thing I noticed is that if the fan's center thing that is solid is not over the heatsink, the noice doesnt happen, so i imagine that it is at some point between the top of the HS (technically the side of the mega where the fans go) and the center of that fan, the airflow is distorted and creates that noise...

I honestly don't know what to do to get rid of it other then to stop using the 2nd fan. One last thing I can do and tested is take a solid object or something with a few holes in it and put it over the top fan elevated about 3-4 quarter coins thick(actual coins, 25cent coins). I took a piece of paper, like a post card thick and sturdy, I can put that those 4 quarters (i can assume 4mm tall) off the top fan and the noise goes away, and some airflow will still go up but now all.
Would this idea of putting something solid about 4milimeters above the top fan to change airflow be a good idea than completely removing the fan?
 

muddocktor

Retired
Joined
Nov 1, 2001
Location
New Iberia, LA
If you are getting resonance with the fins on the Mega, you might try cutting a couple of thin, narrow pieces of rubber (like a bicycle inner tube) and using them to insulate the fan edge from the heatsink fins (like the rubber strips that come with a TRUE) before you clip the wires to hold the fan in place.
 
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Zonnza

Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
Hey mudd, i was looking around for you but noticed ur sig said ur out on the rig, was going to ask you about this since you said you got the same type of fans for your tests. Your not having this humming/buzzing noise issue are you?

I have no idea if this is a resonance issue, i really don't know how it happens. But I can say that if I turn off the bottom fan(the push one) and leave the top fan(pull) on, it still happens.

I tryed a lot of things to fix it but nothing works. I have considered using rubber but I went and took some 1mm thick foam like things that stick on both sides and cut it into 4 pieces for the 4 corners of the fan, and had the fan rest of those so it wouldn't vibrate but the noise still happened.
 
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Zonnza

Zonnza

Member
Joined
Sep 14, 2009
Location
Florida
One other thing Im wondering about is if I might have put the thermal paste on incorrectly cause when I put the cooler on the pasted chip(line method), I had to slide it a bit cause the holes on the mounting system where not aligned. My min temps on realtemp show as 40,39,39,37 as record but while just running a web browser and considering this "idle" im getting 42,43,41,40 On your(mudds) charts even the weakest push-pull config was 36 as min. My high temps at 4ghz don't even go over 72 too (using prime95 or linX). Should I maybe redo the thermal paste and try again? or should I even try repositioning the mega so its oriented pushing air to the back instead of the top and see if that fixes sound issue?