rattling noise when shaking the phone

I believe it's the camera. It's been the case even with my old Galaxy S2 and Lumia 800. NOTHING TO WORRY ABOUT PEOPLE!
 
I was just worries as I head it even when I put the phone up to my ear to talk. It doesn't take vigorous shaking to hear it, just a light movement. That still considered normal?

Could it just simply be the hardware buttons you are hearing?

Dont think so. I've attempted to hold them down and shake it to no avail. I have also pulled the SIM to see if that's what it was with no luck.