On January 2, 2014, u/Redwantsblue80 posted to the r/Ghosts subreddit with a post titled "Experience using Sleep As Android App" They had been using the app to monitor their sleep since October 2013, and while they had been told in the past that they do talk in their sleep, for their majority of their time using the app all they had picked up was coughing and them changing positions during the night. That is, until December 30, 2013:
This night I was sleeping in my bed - my 3 year old was with me that night as he is scared of the dark. It was just the two of us in the whole house. The next night I decided to go through and delete my recordings and saw this particular record. In it, you can [hear] some clicks that start to get louder over the course of the recording. Eventually you can hear me say "What are you doing?" and immediately after there is a deep voice that says "Nothing". The clicks become very loud at that point and at the very end of the recording you hear the same voice say "That's them" (I think). I am pretty creeped out by this. I don't remember being awake that night.
With the post u/Redwantsblue80 attached the recording they had made with the mystery voices on it, and later on someone in the replies posted a 'cleaned up' version that made it somewhat easier to hear.
Replies to the post were split between those thought it was the OP just talking in their sleep - although u/Redwantsblue80 was certain that neither they nor their toddler were capable of making their voices sound like that -, a home invasion, or ghost. Obviously, of those three, the home invasion is the most terrifying, but then again there was no other evidence either for or against that theory. According to the OP, there were no signs of a break-in - and nothing was taken or disturbed inside the house. OP didn't report any other paranormal phenomena happening either, aside from a couple of other occasions when their sleep app picked up clicking similar to the clicking heard in the recording. It was truly a mystery.
Speaking purely from my own knowledge and experiences, I wouldn't have been so quick to dismiss the 'sleep-talking' explanation. Anyone who's listened to a recording of themselves speaking knows that you always sound different from how you thought you sounded. And as someone who has sleeptalked and sleepwalked for most of their life, I know (from being told by others) that I can say or do some weird things while asleep. But at the same time, if u/Redwantsblue80 is certain that this wasn't the case, and the event didn't repeat itself, then we have to believe them.
Which leaves the other two options, one of which is considerably more concerning than the other. Thankfully, as I said, nothing like this ever happened again, and in something of a rarity for Reddit, u/Redwantsblue80 made regular updates to her original post, eventually informing people that on April 21, 2015, they were no longer living at that house.
Whatever it was that u/Redwantsblue80 recorded on their sleep app that night, it definitely scared them enough to go to Reddit and post on the r/Ghosts subreddit asking for advice. And it's perfectly understandable that it would freak someone out - I know it would have worried me, even though, as I said before, I know I talk in my sleep. At least no-one was harmed, and u/Redwantsblue80 was able to move to somewhere they felt safer in, even if we likely will never know what was behind it.
Sources:
"Experience using Sleep As Android App" (r/Ghosts, Reddit)