Sometimes in the middle of the night I get kind of stuck. Laying in bed, not quite awake, not totally asleep, kind of dreaming. And stuck on one particular subject, unable to change it and think/dream about anything else. - recently at Chizumatic

I'm sitting here wide awake at 4:15 am local time having just had this happen due to a bad combination of getting too cold while sleeping (always gives me annoyingly complicated dreams) and probably too much caffeine.

My reward is a rather nasty awakening where my subconscious was making a good run at convincing me an infrequently recurring sound I've been hearing may be an auditory hallucination, which still almost freaks me out to type so I must not be quite ready to go back to sleep yet. It actually took me a moment to establish that I really have a memory of having heard this sound in real life and that the whole thing wasn't a dream-time mental fabrication. The idea that I frequently have a mathematically precise auditory hallucinations does not pass rational muster, but who's rational at 4:15am?

To prove to myself that I'm not crazy I tried to Google the sound, which is not easy, but I finally found something very similar here; it starts exactly the same, but it always ended differently. (Perhaps because I'm almost always directly on top of a tower, or perhaps this is a recording of a data burst where I'm just hearing a simple sync signal.) Since you have to register for that site, here's an mp3 version of the characteristic beginning (I cut off the part that varies for space & bandwidth).

Perhaps you've heard it too. Now you know: Cell phone interference, probably GSM.

Not auditory hallucination. You hear that, subconscious? Real. Can I go back to sleep now? Yes? Thank you.