激動 (gekidou) ?? It's nothing to do with current topic.
btw I might have misled you, sorry. Nantekotta is not usually used in real life, rather in fiction (manga, anime or novel, etc.).
Nonetheless just for your convenience I uploaded my voice.
Perhaps one of them in my previous post seems to suit better. They're Aaa... / Uwa! / Uwaa... / U waa... . Or, Uu... might work as well.
maz