A wah wah
You make this sound when someone says something so dumb it makes you want to scream. You drag the last 'wah' out like you're dying.
'Wah-wah!' he said after his friend told a joke about a chicken wearing pants.
'WAH!' she yelled after her friend said the sky was pink.
He did a 'Wah-WAH!' after his friend said cats were the best.