Why is there a rattling sound when I shake my device?

Question/ Phenomena-1

Why is there a rattling sound when I shake my device?

Mechanism-1

The camera module used for Xperia PRO-I wide camera uses a voice coil motor to drive the lens group inside Lens moving part. 

When the voice coil motor is not powered, this Lens moving part may produce a sound when you shake a device or tap on one of the corners because it cannot be held at a certain position inside the Camera module.

This is not a malfunction and this sound never affects the performance or durability of the camera.

Question/ Phenomena-2

Why do I sometimes hear a click from the inside?

When starting camera app, the phone makes some sound. Users may also feel small vibrations on the phone.

Mechanism-2

When any camera app starts (Photo Pro, Cinema Pro, or Video Pro), the wide camera operates initialization which switched iris between F2 and F4 several times in a very short time.

This makes a blinking sound but assures iris working correctly.

 This is not a malfunction and this sound never affects the performance or durability of the camera.