The noise you can here is the zoom motor stopping and starting and very little you can do about it. The internal microphone is only doing it's job... picking ALL the sound up it detects.
These cameras in the video mode is only a gimmick, the quality of these internal microphones leaves a lot to be desired, the only way round it is to use an external microphone, whether these cameras have that facility I can't say, do consult your user manual on using an external mic.
Dave
