Change in light intensity?

Does your camera make some noise ( from inside the lens) when moving from different intensity source of light? I think it's just an adjustment but i'm not sure.And it also does so when focusing(especially in portrait- best shot mode) It's an Casio Exilim EX Z 600.
Thanks 4 your info.

Focusing, yes - but that's it. I am not familiar with that particular camera so this may or may not be normal. Can't picture what it would be adjusting that would make noise... Anybody out there have one?