The voice comes through to Allura, but soft and distorted, with most of the sound absorbed by the rubble itself. After all, her astral self hadn't left with just her sense of sight, but all which could conceivably still apply to an incorporeal body.

In fact, the disconnect with her physical body is great enough that rather than reply verbally, she finds it easier to send her response telepathically:

"All right. Let me go take a look."

It's again quite a strange experience, moving through so much solid matter again. But she takes that option anyway, since it seems conceptually easier than having to go up and then back down. But before she can see what the familiars have found (or much of anything, really), she discovers it herself by finding something that she can't pass through.

After all, an astral projection cannot possess other living things.

And so, it's only shortly after that she breaks the astral projection, briefly reeling back as if her spirit had slingshotted back into her body. "There's someone in there. They're trapped, but it shouldn't take long to uncover them." As she explains, she rises to her feet, and makes a beeline towards the location to start removing the top pieces.