One of those sluggish heartbeats is quicker than the other. Matt will hear it first--panicked hyperventilating just beyond the door, though the piercing voice only a child who is truly scared that follows it will be loud enough for any of them to hear if a bit muffled.

"Miles?! Come on--come on please!"

He hasn't been able to get the younger Spider-Man to respond for several minutes now and Peter is losing his shit. He's too out of it from the cold to think reasonably, so he's been reduced to holding tightly to the younger boy and wailing. Which, considering the dangers that are lurking out here is not the best solution. It's a damn good thing there's Help finally arrived.