Right...that is a bit creepy, I give you that!!! Since I was eight years old I have been experiencing sleep paralysis and I am not afraid to admit that for the first many years it scared the hell out of me until I got the chance to do some research and find out what really was going. Sleep paralysis is basically the opposite both physically and mentally of deep meditation...so no biggie really. But it does open up to things and sensations that you are normally perhaps not sensitive to and simply therefor do not registre in everyday life. And no, despite what you may think then sleep paralysis is quite common and has known about since time in memorial: the term night mare stems from the Norse mareridt.. which referes to a mare (succubus or incubus creature orr even an old hag) "ridning" you meaning sitting on your chest which referes to the paralysed sensation that you experience during sleep paralysis. And in Asia the term ghost dreaming has been used for centuries to describe sleep paralysis. So regardless of how you feel should you have experienced sleep paralysis then you are far from the only one!
So you say that you start out hearing a static sound, then this sound is mixed with a child's voice, and then you feel a presence of somebody standing next to you... and it takes place in the very early hours of the morning? That sounds a hell of a lot like sleep paralysis to me! Do you feel paralysed when experiencing this? Because if you do then I am willing to bet my life that it is a true case of sleep paralysis!
As to what sleep paralysis is in a metaphysical sense and if you can have the same recurring sleep paralysis experience like a child asking "Are you there?" then I cannot offer any absolute truths: some say that sleep paralysis is nothing more than dreams who have overstayed their welcome so to speak whilst others claim that for a breif moment (and yes, a sleep paralysis experience or attack depending on how you approach it last less than a few minutes even though they can feel like an eternity). But as with meditation which is the mirror image so to speak of sleep paralysis then the astral world will never be able to harm you physically!!!! And finally if you can have a recurring dream then there is no reason why you cannot have a recurring sleep paralysis experience.
There are however a few things that you can do to prevent or trigger a sleep paralysis experience;
Going without enough sleep for more than a day or two. Heavy, deep, and dreamless sleeping as a result of a period of too little sleep is, if you are prone to sleep paralysis, an invite to just that because the last cycle of the REM sleep in a normal sleep rythm tries to compensate for the lack of REM sleep the previous nights/days and there for goes a bit overboard.
Eating too much - and too heavy food just before bedtime
The after math of an aura migraine
Now I am not saying that what you have experienced is all due to sleep paralysis...full stop!!! So if we assume that it is not the case, then is there any way that you can record this sound phenomenon? Because if you do manage to snatch up anything then no, it is clearly not your mind which is a bit off. And I would also look into this infrasound if I was you as itt seems like something that could trigger sleep paralysis too. Do you know of any recently newdevices or occurences near you that might be the cause?