The real iphone device has an hardware sound switch, if i turn the switch to off (bottom position), all sounds form MediaPlayer{} turns off.

This shall be not expected behaviour, this switch does not mean to kill all iphone sounds, it is only for iphone RINGING sounds...

As far as I remember, in 6.7.0 (but that time it was also lower verison of Xcode and iOS itself) this didnt happen (unfortunatelly cant recall 100%).