The clapping gets his attention, alright. Just as he's about to bring his foot down dangerously close to where Frisk is standing, Starscream freezes, lifting his foot away and peering down.

Ugh, he almost stepped in people! He scowls, flares his wings, and jabs an accusing finger in Frisk's direction.

"You! Human. Where are we?"

He'll deal with the seen-by-people thing later. The jig is obviously already up.