Fan Noise

[FlutterGuy]

This is a strange one... I have a Casecom 6788 case, and a few 120mm fans. When I install one of them on the side panel as an exhaust it runs fine. But when I install it in the same place as an intake it makes a vibrating sound. I've tried it with all the fans, they all do it to some extent. The really weird thing is that the same fans installed in other places as intakes do not make this noise.

Has anyone encountered this sort of issue before, or have any idea how to fix it? The noise is driving me crazy!

Thanks,

John (FlutterGuy)

 

[g048989h]

The vibration is caused by the additional airflow into your case I think. Is it the fan that is vibrating? If so, some rubber grommets may fix it.

 

[IH8U]

+1 to the rubber grommets, however what is the model of the fan you are putting in? What is it's CFM? Some fans with higher CFM are heavy on vibration (as they spin at higher speeds) also make sure the blades aren't rubbing/contacting something (ie a grille, shroud, case ect...).

 

[genghiskron]

it could also be that the thrust from the fan is causing the whole side panel to vibrate. see if placing your finger on the frame of the fan reduces noise. also see if placing your hand on the side panel reduces noise.

 

[FlutterGuy]

Thanks for the replies.

I've just realised that covering the fan (i.e. preventing airflow onto it) stops the noise. So you're probably on to something genghiskron, it looks to be caused by airflow interacting with the side panel. It's a very localised vibration though, the only way of stopping it is to place my hand on the grill that covers the fan mount, hence defeating the point of having a fan... I might just have to live with it :-(

@g048989h, I've tried the fan with and without grommets, they had no effect.

@IH8U, It's a fairly budget fan, it didnt have specs on airflow. But based on how big it is, how fast it's spinning and specs for similar fans I'd say its pushing 30-40 CFM, which shouldnt be too high. And the blades are definitely unobstructed.

 

[FlutterGuy]

After some more research and testing, I've found the source of the problem: the tips of the fan blades are moving very close to the grill covering the fan slot. As a result, there is a lot of localised turbulence, and this is the source of the noise.

Solution: find some way of offsetting the fan from the case. Even a few millimeters drastically reduces the noise. I mount all my fans using nuts and bolts, so the problem is trivially solved by putting a couple of extra nuts on each bolt, between the case and the fan.

I hope this helps anyone who might be having a similar issue.

 

[genghiskron]

btw, your case is also branded as the rosewill challenger. on my case, an antec 300, the fan grill is bulged outwards, and i had always kinda wondered why it was designed that way. now i know.