He'd settled on the strangest though of a loth-cat endlessly running, chasing a speck of light. Then he could easily account for any noises.
But the noise he heard was Anakin sighing.
Obi-wan cracked one eye open and glanced up at the other. "I didn't expect you to come out here." With eyes closed again, he asked, "Are you through with your fun for the evening?" It was a genuine question, no malice or sternness of an upcoming lecture to his tone. He wasn't intending to intrude. Perhaps he simply had a question.