Case changed the voice quality

Unfortunately, only 1 star. The bag is indeed processed super and looks elegant, but unfortunately it has one major drawback. On the back of the SII is another micro to background noise filter. The Micro is not covered, although the shell around the micro seems to change the acoustic properties, so that my interlocutor is heard twice (Hall). Not the point. At first I thought my phone was broken. Without envelope is again everything OK