loud case hum...how to silence?

I have 5 Kingwin fans attached to my case, two of which are on the side.

http://www.newegg.com/Product/Product.asp?Item=N82E16811999964

That's the fan.

My problem is that when the fans are running on the side panel, it makes a loud, low-pitched hum.

The stock case fans that came on the side did not make this noise, but they were no where near as powerful as the kingwins.

The kingwins themselves are as loud as the stock case fans, which were dead quiet, it's just that they seem to be too powerful for the side of the case and its causing the aluminum to vibrate enough to make this noise.

An mp3 of the noise is attached.

Is there anything I can put on the case to eliminate this noise?

 

with higher air flow you have higher rpm's and with higher rpm's you have more vibration...... and what are you running that you need 5 high speed fans?