Ay! is the sound I make when I feel foolish - I've walked into a wall, because I was daydreaming, I've forgotten something or I'm just feeling frustrated.
 
Yeah Wha'eva! is when you get so comfortable with someone that you begin to lose your filters and start to tell them what you really think!
 
Blah! Blah! Blah! is that person who just loves the sound of their own voice. The talk incessantly about nothing in particular for no good reason and after a while their words begin to merge into a kind of background noise.