Well, quarrels will definitely be heard.
Who can quarrel out of earshot of their children while speaking/shouting so loudly must be a pro.
But they should at least have taken the liberty to NOT quarrel in front of their children.
It could have some bad influences on the children, you know.
Like, say, cos the child's parents always quarrel in front of her, and she is sick of it and hates it damn much that she decides - in order not for that to happen to herself - never to marry in future.
What's more, if the parents almost never quarrel when she's not around(but how would she know? Cos they still talk to each other when she gets back from school or somewhere), and only quarrels when she's around, then she may think that she is a jinx.
And that sure is not too good for the child's development.

So parents or parents-to-be out there, or whoever is single but wants to be a parent in future:
NEVER, EVER quarrel in front of your children.
 Don't be like some stupid girl's sucky parents.