In Italy many people complain about a rustling sound when a call is made (and not when you answer a call). The same noise is present when listening to mp3 or use youtube and you can notice it clearing the audio.
That rustling sound you can notice it more using a headset.
You can also delete it temporarily, while outgoing calls, going to change the sound volume in the settings (even after adjusting the alarm volume, the rustling sound disappears!).
I think it's a software problem in the firmware of LG and if other countries do not have this problem, this is a firmware issue dedicated to Italy.