online Collins dictionary aah INTERJECTION 1. used to express surprise, delight, etc. VERB INTRANSITIVE 2. to exclaim with surprise, delight, etc. they oohed and aahed at the baby ooh EXCLAMATION People say 'ooh' when they are surprised, looking forward to something, or find something pleasant or unpleasant. [informal, feelings] 'Ooh dear me, that's a bit of an unkind comment, isn't it?' 'Red? Ooh how nice.'

It's the sound we make when surprised, or being told something, maybe learning something. It's like aawww, for something cute. The ooohhh sound is more so ooo, not oh, if the 'h' threw you off. It's sometimes a bit of a joke, it has been used a lot in shows where a magician shows something not so great, asks for an oohhh, shows another thing underwhelming, you know to respond with ahhh, but then he really surprises you. Happens at faires and such.

The expressed delight amazement pleasure: basically they reacted in the way that people often react when they see a newborn baby.,😊

Those are the sounds people make when they see something amazing like a dinosaur skeleton!