Ron’s voice trailed away in mutters, barely audible over the loud crackling of the fire, though Harry thought he caught the words "Krum" and "Can’t complain" again.
"Mr. Gaunt, please!" said Ogden in a shocked voice, as Merope, who had already picked up the pot, flushed blotchily scarlet, lost her grip on the pot again, drew her wand shakily from her pocket, pointed it at the pot, and muttered a hasty, inaudible spell that caused the pot to shoot across the floor away from her, hit the opposite wall, and crack in two.
I take it," he turned, smiling, to look at Hermione, who had let out an audible gasp, "that you know what Felix Felicis does, Miss Granger?"
My God, what an eyesore!" rang out a girl’s voice, as clearly audible through the open window as if she had stood in the room beside them.
There are no more uses of "audible" in the book.
Show samples from other sources
She spoke in a barely audible whisper.
It was so quiet, our breathing was the only thing audible in the room.