Sound not working macbook pro - intermittent
Yesterday, the sound on my computer was not working. Volume was turned all the way up on computer and iTunes. I restarted and the boot up sound was very quiet. Once, I logged in, I turned the sound up and the sound worked fine. Today, the same thing happened - no sound. I haven't tried restarting yet because I now believe it's a more serious problem. Any help?
MacBook Pro (13-inch Late 2011), OS X Mountain Lion (10.8.1)