If you have an older PC and are tired of it sounding like a jumbo jet taking off, then you could check out the Acousti Deluxe noise reduction pack.
Inside the box - which weighs 3.1kg - you get 3 pieces of pre-cut foam, two of which can be placed in vacant 5.25" bays and one in a 3.5" bay.
Plus there is 3 pieces of Acoustic composite self-adhesive backing sheets, that can be used on the case sides, roof and floor. One of which features an AcoustiContour anechoic surface - just think of a carton of eggs and you can visualise the shape of the material.
As you can tell the sheets of foam will add weight to your PC, but it does depend on how much of the material you use.
To start with we gave the pack the near impossible task of quietening down our ancient server case, which has more metal than a mammoth tank and more holes than a rabbits den. To put it bluntly it was a breeding ground for noise.
More so as we have five 3.5" hard drive bays, one floppy bay, five 5.25" bays, a top section with a noisy 80mm fan, a PSU with a 120mm fan, a CPU with a giant 120mm fan and a bottom 80mm fan placement (which was vacant but the holes were still there). Oh and each side panel had its own ventilation.
Adding the composite sheets was amazingly simple and we used a kitchen knife a piece of wood (with a straight edge) and a pair of scissors to cut the material. But before you rush in and place the sheets all over the place you need to sit down and plan where you want the sheets to go. For example you need to ensure that the material does not cover any ventilation holes or block access to your cooling fans, plus you need to ensure that you can actually close your case once the material is on! - trust us we made this mistake.
Even if you do make a mistake you can refit pieces a few times before the adhesive becomes useless and as an added bonus we found there to be no sticky residue left on our case, which is useful if you do decide to replace or fit it to another PC.
The pieces are large enough to fit a server case so you do get plenty of material, for smaller cases you can probably do a fair few PC's with one pack.
We spent a week or so playing around with different placements of material in our server case and we admit it took us a while to get used to proper placement before we could finally hear a reduction in noise - which was a blessing indeed. We took this experience and stuck two small pieces of material inside our Antec case (which still featured 1 large 120mm fan and one 80mm, plus a noisy CPU fan) and we heard an instant reduction in noise and this was a silent case to start with.
However you need to remember that the AcoustiPack is not a complete solution, you still need other methods to reduce noise, for example in our server case we had a hard drive noise reduction kit that we will be
reviewing separately and a couple of dampening screws to reduce vibration.
Also you need to monitor your PC's internal temperature as it does increase, we found our system temperature went up by about 4-5oc during a windows sesh and slightly higher during a heavy gaming sesh - but we did have a lot of material in our test server case.