new noise

So finally getting my boy settled in with only one set back transferring to his new cage. The last few days we have heard an odd noise that we are 90% sure was the chinchilla. It sounded like an old creepy door squeaking open. I actually got out of bed to make sure it wasn't any of the doors. The only thing out of the ordinary was Darwin sitting quietly at the front of his cage. I talked to him and he quickly smelled my nose before going back to bed. And my fiance heard the same thing the night before.

Does anyone know what this noise means? It's not a bark and it's not a sharp noise. He doesn't seem to want anything when we check on him. I'm just concerned it might be pain. He looks fine but he has such a sad past.

Thanks for any input.