In the story that the narrator is reading, Ethelred beats open a wooden door. What does the narrator hear in the house?

From the text:

At the termination of this sentence I started, and for a moment, paused; for it appeared to me (although I at once concluded that my excited fancy had deceived me) — it appeared to me that, from some very remote portion of the mansion or of its vicinity, there came, indistinctly, to my ears, what might have been, in its exact similarity of character, the echo (but a stifled and dull one certainly) of the very cracking and ripping sound which Sir Launcelot had so particularly described.