Friday, January 16, 2009

Reducing Hard Disk Noise / Vibration

To date I hadn't put too much thought into the dampening of the hard disk noise.
However with the initial joining together of all of the pieces, it seemed that one of the noisiest parts was in fact the hard disk. So, I thought it worthwhile at least having an attempt at doing some dampening.

So far, the hard disk has been simply bolted to the bottom sheet of metal. From what I have read, this is probably the noisiest way for mounting the hard disk.
One of the quietest ways is to mount the hard disk in a set of elastic strings - kind of like letting it float around in a spider web.

Given the limited amount of space available for the hard disk - suspending in elastic wasn't really an option. So after scanning around the house, I found some foam sponge that hopefully would help. The foam was left over from sealing up around the windows this winter :-)

The basic plan was to attach two strips of sheet metal to the bottom/sides of the hard disk, as shown.



These sheets of metal are held on with screws, which are also used to attach the foam - as shown here.



In this view the hard disk is upside down - so basically when you flip it over, you bend the foam so that it isolates the bottom of the hard disk from the base on which it is mounted, and you would also get some isolation from the sides due to the foam (the foam is a little wider than the screws). Here is the hard disk up the right way now.



So it seemed to be going to plan OK - until I did a test fit. The disk was too wide now - by just a few mm's - to fit next to the mother board :-(



The mother board ended up resting on the screws in the sides of the hard drive.

So - plan B - move the screws to the bottom side. There was more space available in the vertical direction.



The same as before - the screw heads are below the level of the foam (just), so when resting on the base sheet of metal, there is clearance. Maybe with time the foam will compress - but then can just re cut some slightly thicker foam. With this arrangement, there is now just enough space left between the motherboard and the disk.



The final step is to attache a guide piece of metal to ensure that the hard disk stays over against the edge of the base - clear of the motherboard. A simple low bent-up piece of sheet metal is to be used.



Once attached with rivets, and the disk in place, it seems to be reasonably well seated.



With clearance (only small) between the disk and motherboard - and from the top of the disk to the power supply when mounted.




There is also sufficient gap between the added guide piece of metal (and rivets) and the motherboard.



So that is the basic dampening.

I did some quick sound testing...
Basically, the dampening does seem to quiet noise I am hearing.
Looking at the spectrums for various listening locations... where the left had spectrums are without dampening - directly screwed to the base, and the right hand ones are with dampening.



From the spectrums perspective, the damping actually seems to increase the noise levels between around 10's ~ 700 HZ. However in the range from 700 HZ upwards, there is a noticeable decrease in the noise levels.
Overall, the dampening seems to have a positive impact on the noise perception.

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