When i shake or move fast my xperia v something sound inside. Not the buttons of volume or the switch on button because i press them and still something sound...dont know if i should go to the shop to use the guarantee or its normal...
Mine makes a sound too, but i think a thread like that was already discussed here on XDA and lots of Xperia V users said that they phones too have a sound when shaked.
I bought mine on April, 2013, It's working a 100% fine.