I see this hasn’t been checked so far, so -
what lead are you using to connect up your sound?
The RPi2 has, like the B+ a 4 pole connector which provides both video and audio, and you can get some odd effects if you don’t use the right poles.
There are several different types of wire lead on offer, and one which works for an Apple device will for this (if I recall correctly).
Somewhere there was a picture of the wire types with comments
I hope I got that posting right - haven’t tried a pic before
Derek