Bluetooth headphones coect but play no sound

I'm ruing Ubuntu 14.04 on a Acer Aspire R5-471T.

I try to coect my Bluetooth headphones to my computer. When I do, they make the noise that says they're coected, but after that, won't play sound. The Bluetooth icon in the upper right appears with a little lock under it. In the sound options, the dials that would let me adjust left and grey balance are grayed out. When I try to play something with Google Play Music, say, the play button doesn't respond and become a pause button, and similarly with YouTube. When I discoect the headphones, the videos or audio tracks start playing.

These headphones work for my phone, so it doesn't seem to be a problem with them.

How do I make them play sound?

Thanks!