first, you must locate the source of the noise you are trying to get rid of.
is it vibration: an exhaust fan or a ballast that is srewed to a wall will cause extremely loud noises that reverberate throughout the house. this is fixed by putting cheap rubber feet under noisy ballast or fan then attach to wall
also, remember noise has frequency just like light. the freqeuncy of sound requires different baffle techniques.
low frequency sound requires a solid baffle to dampen the unwanted noise.
high frequency sound requires soft baffle to dampen unwanted noise.
the best thing to use if you have the cash is a product for heating and air conditioning called " duct board "
it comes in 1" to 3" thick, has high r-value, its coated with silver paperfoil on one side, its made from fiberglass, it is both solid and soft, and it can be cut to size with a pocket knife.
it is the same stuff that companies use for home theaters and to sound proof conference rooms.
i think it is around 35 dollars us. for 4ft. x 10ft. sheet.
hope this helps... and if it is ghetto noise damping that your after, the best thing is comforters from goodwill or salvation army or flea market... they help a lot on a budget. just nailem up and your done.