Ignoring Hermione's emphasis on the words "Professor of Defense Against the Dark Arts," Lockhart looked to her for help as though she were his savior.
"What voice? Harry was just joking with me, weren't you?" he hastily asked for confirmation, hope in his eyes.
"Yes, Harry was just teasing you."
Hermione nodded.
"But!"
Harry grew anxious too.
He really had heard those hoarse whispers, but apparently neither Hermione nor Lockhart could hear them, which made him panic.
"All right, whatever it is, we can talk about it later."
Hermione waved a hand, calming Harry down, then turned to Lockhart.
"Professor, you've been writing letters for over four hours. You must be tired by now. It's time to go back to bed."
At that, Lockhart hurriedly stood up.
"Yes, yes, I should go back and rest. I have to teach you tomorrow."
Despite having received Harry's answer, he still felt that the classroom had suddenly become eerie, and he couldn't wait to leave.
Scooping up the letters on the desk, Lockhart fled as fast as his legs could carry him.
Once Lockhart disappeared through the doorway, Harry finally spoke.
"Hermione, I really did hear someone talking just now. You have to believe me."
Hermione said helplessly,
"I never said I didn't believe you. But so what if you heard it? Neither I nor anyone else can hear it. Going around telling people now will only make them think there's something wrong with you."
"Even in the magical world, hearing things other people can't hear isn't a good sign."
Naturally, she knew what Harry had heard.
There was only one creature at Hogwarts whose "speech" only Harry could hear, which liked slithering through the walls while running its mouth the entire time.
That was the basilisk kept in the Chamber of Secrets.