Does any one know any material that provides good sound isolation?

i was thinking something like a foam, and what kind of foam would be better? i need this material for a pc, well the cpu case, from being to noisy, so light and cool materials are prefered, i also understand that a surface with hills and valleys helps absorving sound, is that true?Does any one know any material that provides good sound isolation?
I guest you can use cork . Yeah , Donna is a genius .





yeah , you can covert the walls with cork and the door in your room and the cork is good absorbing noise .





Just don't put cork in your windows because if the AC stop working you will will not be getting air then .





Yess , that it , cork .Does any one know any material that provides good sound isolation?
try cork.


not only is it a sound barrier it acts as an insulator as well
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