I have had Mint 12 with Cinammon for sometime now. Sound was working great... in YouTube, Banshee... etc. Yet, maybe after an automatic update (I'm not sure), problems begun. Within YouTube whether its in Firefox or Google Chrome, when the music/track sound goes up, the little speaker icon in the panel bar shows variations in volume levels. I get into the sound control when the problem shows up, and the sound control by itself goes down on high sound pitches or output and then goes down again. Its spoiling sound output... It happens in Banshee as well; I instaled Amarok in Mint 12 Cinammon... and the same.
I tried this with Mint 13 (KDE and Cinammon), and ther is no such a problem ther. What could it be?