Ballast noise?

[Wilty]

I have a TAR ballast powering my newly installed 250W MH. Got it all wired and then plugged it in. The bulb fired up and it went well. BUT. . The ballast is humming. I know that it is vibrating a little bit but does anyone have a solution for me to get the ballast quieter? Its loud enough for me not to use it. I think i am going to try mounting it on a high heat rubber to absorb the vibration. Anyone had this trouble?