Instructables

Reducing Fan noise of a NAS device.

Wow, my first instructable so please be gentle.

My home network contains, among other things, a NAS device.
This is a device that you would run 24x7 for general availability right ?
However I prefer to keep this device in the living room, because that's where the 1Gb ethernet switch is located.
After a couple of months the noises that the device produces became too loud and annoying, so time to call in the help of Tinkerboy.
 
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Step 1: Find the noisy component.

Well the high pitch whine told me it was either the disk or the fan.
Upon opening the case (oops there goes the warranty) I did a swift aural inspection with the NAS running.
In fact the noises had two sources:
-the vibration from the hard drive
-a cheap small fan running at full speed.

Step 2: What to do about the fan?

The disk vibration was actually caused by loose screws, so that was easily fixed.

Next the fan: how to reduce its noise?

I could think of the following options :
-replace with quieter model
-reduce fan speed.

I opted for the second, knowing that the spare small fans I had were equally noisy.

The preferred option would have been to get a smart speed control, but this would have to be completely self-supporting and a design was not readily at hand.

So eventually I opted for the simplest: reduce the fan speed by adding a resistor.
This reduces overall airflow so introduces the risk of overheating. But the NAS webpages show the temperature of the disk, so I decided I could monitor if cooling is sufficient using that information.

Step 3: Deciding on the right resistor.

To decide what would be the right resitor I simpy expermented.
I hookd the fan up with a 12 powersupply and added some resistors to find the best result as far as noise and reasonable fanspeed were concerned.

I found a 56 ohms resistor (green-blue-black-gold) giving sufficient speed reduction to get rid of the whining noise while maintaining a reasonable fan-speed.

I also took a small piece of white insulation to fit tightly over the resistor, so none of the bare metal can cause any problems.
omnibot3 years ago
Good job. In my homemade FreeNAS i added a variable 5w wirewound resistor in series to optimise cooling/sound ratio. Works well.
altaria19935 years ago
Wouldn't it be even better for both the cooling and noise to just put in a bigger fan? I don't really know how big that one is, but you should be able to put a 140/120 mm Antec tricool in there, which are silent, and you can easily change the fan speed if it gets too hot.
tinkerboy (author)  altaria19935 years ago
Well my solution is free, and this case fan is a tiny 40x40 fan. I don't know of any such elegant solutions in that size. Modifying the case for a much larger fan would have quite an impact on the design. Your comment does remind me to add some scale reference to pictures in the future, just to show what the size of things are.
frollard5 years ago
Awesome project - My initial thought is nix the fan, and nix the outer case for one with a bajillion holes in it. Enter: the drill press :D
benjgvps5 years ago
I did a similar trick to silence the 5.25" USB to IDE enclosure I picked up. Though, Instead of adding a resistor, I just unplugged the fan entirely. No heat problems!
tinkerboy (author)  benjgvps5 years ago
That's ok if the enclosure can transfer the heat without internal airflow. Makes you wonder why they added the fan in the first place. Maybe for 'old' disks that are less energy efficient? This NAS device also contains a small computer (cpu/memory) so I don't trust it to dissipate all of the heat without active airflow.