Sound quality observation and a question.

[GamerZero]

I've noticed while playing games on my new Nexus 7 (32GB) that you have to turn the volume up about have way to kick in the surround sound affect, at lower volumes though the sound is not as crisp or clear, however the sound is better then on my old last years's Nexus 7 modal because I noticed when playing Dead Trigger and Star Wars Pinball on the new Nexus 7 I'm hearing sounds from those games that I do not remember hearing while playing them on my old Nexus 7, for instance in Dead Trigger I can hear voice-overs from the Charater that you play that I don't remember ever hearing on my old Nexus 7 modal while playing that game, same goes for Star Wars Pinball I'm hearing sound affects I did not hear before. I have a question, when you raise or lower the volume on the new Nexus 7 there are two bars that appear on the screen, one is the sound level bar but what is the bar underneath for?