Is this the sound of a dead battery?

I'm planning on buying a new battery in the morning unless someone thinks it might be something else (alternator?). Interstate MT 51 battery is 2 years and 4 months old. Car sat for only 2 days. Was working fine until tonight.
http://www.youtube.com/watch?v=VdndrUTS5pw
And can I test the battery with my Radio Shack voltometer? Would I set it to the 2:30 position at 20V DCV?
http://i1316.photobucket.com/albums/t620/LegoLand7/radio_zpsb3be2006.jpg

Sounds pretty weak thats for sure. Funny grinding sound winding down towards the end. Check the volts of the battery just how you thought, if thats not it, could be starter that grinding sound didnt sound very nice.

Besure to check connections for corrosion or bad wires, that can make a good battery seem bad at first. Im leaning towards battery, but starter next if battery comes back good.

Stuck a new battery in there. Works great now. Hopefully it keeps charging as it should.