The Question and Answer section for Jane Eyre is a great resource to ask questions, find answers, and discuss the novel.
From the text:
"I did," said I, dropping my voice, so that Leah, who was still polishing the panes, could not hear me, "and at first I thought it
was Pilot: but Pilot cannot laugh; and I am certain I heard a laugh, and a strange one."
Jane is kept awake by the thought of Rochester visiting young, eligible ladies.... particularly, beautiful, young ladies.
I think he was startled and was not sure what was happening.