I have a pair of speakers plugged in to my computer, and I often use earphone, if I plug in my earphone, my system will automatically make earphone works as a default sound device, that means, my software will play all sound through my earphone. And if I plug off my earphone, it play sound through my speakers.

When I start minecraft with earphone plugged in, it play sound normally through my earphone, and when I plug off my earphone, it play sound through my speakers, and when I plug in my earphone again, it couldn't play any sound, just become silence, even I turn off the volume in minecraft menu and turn it to 100% again, it will never make any sound, until I shutdown the game and run it again.

When I start minecraft without earphone plugged in, it play sound through my speakers, and when I plug in my earphone, it becomes totally silence.

Other software, like `foobar2000', can play sound normally, if my earphone plugged in, it play sound through my earphone, and if my earphone plugged off, it play sound through my speakers.