Seeking to avoid being seen by his fellow students, Harry roamed around Hogsmeade in his invisibility cloak. At one point, he had to get past a single girl in his way. He walked slowly and carefully past her, but she turned around and said, "Harry? What are you doing here? And why are you walking so quietly?"
"W-what?" he stammered. "How can you see me? I'm under the invisibility cloak!"
"I'm BLIND, you prat! The way you walk is like a fingerprint to me. You didn't think I'd be able to HEAR you?"