Some music videos on YouTube are available in more than one resolution.
Do they all have the same audio quality? Or do the videos with larger resolution have better audio?
Wikipedia has a table with different conversions and also the audio related to them.
As of Jan 2013
I'm sure the sound quality might have to do a lot with flash player as well, but I'm no expert on that.
Here's a detailed list for audio qualities for different video qualities: