How to get a PC quiet by using soundproof mats
 

Silent case fans, CPU fans and graphics card fans are a way to get a PC reasonably quiet, but even the quietest fans still produce an audible noise. Some manufacturers have developed sound proof mats to be placed on the inside of the case panels of a PC to reduce the noise made by gans even further. The mats usually have a self adhesive side, and there are sets available especially designed for specific cases. The generic sets however contain a number of large mats that can be cut down to size with a hobby knife and placed in to the case. We have tested three widely available kits to see if using mats will actually improve the sound levels of a standard PC.

http://www.hardware.info/en-UK/artic...lence_your_PC/

not quite, 10 dBA is twice as loud; 3dB is twice as loud; in the test setup they mention they measure in dBA, and then show results in dB? I think they just forgot a letter ;)

What did you expect from people trying to quiet down a PC the wrong way?

Sound proof materials do help; I have been using it since early this year. The material I found that worked well came from the underlayment of hardwoord floor (the non-fiber type) high density foam type; it is thin enough for the side panels.