I find the opposite. My birds make that noise when they are hungry, bored, irritated, have to lay an egg ("Get this thing outta me!!!!"), or generally, when they want something. I've always thought the happy noise was less 'run-on', lighter, and more mild.
My game birds make that noise, it seems like it happens mostly when they think that they're missing out on something or are getting a really good treat. It would be a happy sound for them.. I swear I have peacock's in disguise with these girls.