Really worried, just heard one of my crabs chirp (AUSSIE)

[Nibbles407]

Background info:
I have 4 crabs, have had them almost 2 months now, there's one big one (bit larger than a ping pong ball in shell), 2 medium size ones (half the size of the big one), and one tiny one (half the size of the medium ones). I have them in a reptile one rtf 900, that I've turned into a 2 story set up due to the substrate being deep I wanted them to also have lots of climbing things.
The largest one looks to have had a successful molt (was down about 3 days after arriving, is an orange/peach colour instead of beige, looks bigger too!), and has been up and about for almost a week now. The other 3 have been down for a little over a month. I know they haven't been up as I have a security camera that lets me check on them so I don't stress them out while they're settling in.

I was just sitting, reading, next to the habitat and I heard very quiet, but unmistakable chirping - exactly like the videos/recordings!
At first I was so excited, because I figured they'd be so quiet I'd never hear them. But then I got worried because I've read it can mean they're trapped/attacked.

Please comment any and all advice/info you have on Aussie hermies chirping, I'm really worried.
TYIA

[wodesorel]

I've had molters get loud seemingly at random before, both purple pinchers and Ecuadorians as I'm stateside. It's disconcerting to hear noises coming from under the substrate but it worked out okay. I don't like to dig unless I have a good reason to suspect something went wrong. Your topside crab could also be giving warning blasts, or just trying to figure out where any digging sounds may be coming from, as they will rarely chirp to communicate with each other directly. Generally if they're being attacked it sounds like you would expect a panicked animal to sound like, forceful, scared, screaming.

[Nibbles407]

So it turned out one of the medium ones was ready to come up! But you're absolutely right, it is quite disconcerting. I'm still a little worried about the other 2 who I still haven't seen yet (another med, and a small one), but I now have soooo many shells, and a heap of yummy foods on rotation, so when they're ready/able they'll have all they need.
I'm basically going to not dig ever unless there's flooding or bacterial blooms, as I have read they can be very happy burrowing before and after molting and it's possible they've been topside but I just haven't managed to see them on my camera.

I would love to be able to see how Purples and Ecuadorians are, I've read many fantastic experiences of them. Sadly, though understandable, it's just the Aussie hermies for me