compact flourescents buzzing

I recently pulled out my 2 CF lights to make sure they still worked, I plan on using them when I convert to a salt water tank. Previously they were used for less than 3 months on a planted tank using 6700k bulbs last year.

Well when I plugged them in yesterday there was a very annoying buzzing sound on both of the fixtures, seemingly coming from the location of the fans. I took out the bulbs that were in there and put in the 10,000k and acintic bulbs it came with and there was no change.

So my question is, do CF lights always make this buzzing noise and I simply dont remember hearing it before or has something gone wrong with them? I tried taking the fans out to make sure they didnt have dust or something clogging them up but on each fixture there was atleast one screw that I couldnt get out.

ive smacked it plenty good

do you think its the bulbs, or the fixture itself? i really dont want to have to replace the fixtures, i paid somewhere in the ball park of $200 each and they are essentially brand new.

but in my case? do you think i need to replace the whole unit?