Ways to Quiet Case Fans

[iceblade2097]

I have an older computer that uses 3 80 mm case fans that are a tad loud.  I am looking for a cheap way to quiet them down a smidge.  The fans are quiet till mounted so the sound is from the vibration against the metal case. When looking it looks like there are three choices silicone washers, rubber mounting screws or a rubber gasket.  My questions are:

 

1)Do any of these add ons help quiet the fans?

2)If I went with rubber/silicone washers do I have to use a rubber mounting screw to prevent just chewing the rubber/silicone parts up with the screw threads?

3)Any pros or cons from any of those options or are they all pretty much the same?

4)Any other ideas to quiet the case fans?

[jnkokseby]

Noctua has 80mm fans that should include a silent adapter. They cost a bit more compared to other fans though. They also include rubber mounting "screws" for the fans.

[WoodenMarker]

Yes, they can help dampen vibrations and lower noise. 

I've had the best results with rubber mounting screws. 

Washers are meant to be used with normal fan screws.