I have a 17yo DS and a 10yo DD and they argue all the time!
He teases the life out of her she annoys him when his friends are in, he will sit and stare at her till she screams at him, she will say things like "I've been in your room" (he hates anyone going in his room)
On and on it goes, but on her birthday last week he was nice to her and gave her a cuddle
she told everyone that her brother gave her a cuddle and it was the best present ever 
As much as they argue, fight and tease I know that they love each other really, it's normal, part of growing up and unless things get violent I would leave them to it as much as possible.
Oh and in case your thinking they will grow out of it, be prepared, my eldest 2 are 26 and 28 (both girls) and still bitch at each other occasionally, then both complain to me about the other.
Maybe by the the time they are in their 40's they will stop 
I think ear defenders are a great idea, might get some myself 