I was extremely dissapointed when I first experienced this on my XL1s cameras, I shelled out a lot of canadian bucks to find all my soundtracks destroyed by; furnace noise, zoom noise, physical hands on the camera noise, camera tape transport noise...... it was maddening
I figured out that 90% could be eliminated by a good microphone shockmount installed on the standard light/flash adapter, and 9% could be eliminated by the application of a 'denoiser' filter (properly adjusted) in my editing software.
The other 1% of ambient noise (my knees creaking and popping...) get massaged in the edit or cut.
If your microphone is 'hardmounted' to your camera but is not 'hardwired' you might try this solution.
hope this can help