I've got a set of studio headphones that I use on my MBP all the time with no noticeable "static" while music is playing.
With that said though, keep in mind that any speaker that is in a 'ready' state will likely emit some form of sound (a hum, slight hush, whatever you want to call it). This is due to the power that is going through it. Just turn on your stereo or anything else; hit 'play' then 'pause' on a CD so that nothing is being output, and turn your speakers WAY up.. you'll hear the same background noise most likely. It is just a bit more noticeable when you have the speakers (i.e. your earbuds) directly in your ear canal.
Now, if this is actual static, not just the humming of electricity, then that's a completely different thing altogether.