I conducted a three-day experiment, looking at the role of brainwave synchronisation in insomnia and sleep. The piece I used was natural_sleep_1.bw. This piece goes for 47 minutes. Its design is based on analogy with actual EEG patterns seen in sleep. It has a constant-frequency theta section at the start, intended to encourage the listener through stage 1 into the theta-dominated stage 2. It then ramps down to low-frequency delta waves, mimicing the normal transition to stage 3 and 4 slow wave sleep (SWS). It spends a short time there, then goes back up to theta, then down to delta. The program ends in the second delta segment. If this sequence formed part of the typical sleep cycle, the listner would be expected to ramp up to REM sleep over the half hour after the program completes.
At 1 am, I put on some headphones, started the program, and lay down on my back. Maybe half an hour into it (I suspect during the first delta-wave portion), something odd happened. I had a sleep apnoea episode. My long-term memory wasn't working during the delta-wave state, but I could remember about 5 seconds back into it. I could feel my tongue in the back of my throat. I didn't feel an urgent need for air, I just had a vague feeling that something was wrong. Then a few things happened at once. I swallowed, my tongue moved forward, and the bad feeling went away. My awareness level shot up. Usually this is not something one can measure with any objectivity, but in this case there was an obvious cue: I suddenly became aware of the hissing sound coming from my headphones. A few seconds before I had been completely unaware of it, but now it was loud and my attention was focused on it. I don't remember snoring, although that almost certainly preceded the apnoea.
This was a very exciting discovery. I had no idea that I was prone to that sort of thing. I knew I snore when I lie on my back, but apnoea? In a very chuffed state, I decided it would be best if I rolled over onto my side. I remember feeling uncomfortable from the headphones another couple of times, and then I fell asleep.
The next morning, I was bright and alert 7.5 hours after the program had started the night before. Usually I need 8 hours before I can drag myself out of bed. My headphones were off, but I don't remember taking them off. I went to university and told a few people via IRC about my apnoea discovery the night before. They seemed to think a discovery of apnoea was a bad thing rather than a good thing. Bah! What do they know. I looked up some information on the web and found that a (perhaps outdated) clinical definition of sleep apnoea is that it's only a disorder if it happens more than 5 times per hour, and for more than 10 seconds per episode. Otherwise it's "normal".
That afternoon I felt a bit tired.
This time I found some bud earphones to use. They proved to be very comfortable when I was lying on my side, I barely noticed them. I was quite tired when I started the program, although it was the same time of day as when I had started the night before (1 am). I fell asleep very quickly, I couldn't remember anything past 5 minutes into the program. I woke up the next morning and reached a state of full consciousness 8 hours after the program had started the night before. I wasn't as alert as I was the previous morning.
Friday at university didn't go so well, I felt quite tired in the afternoon, feeling inclined to occasionally rest my head on my desk. There were some twinges of mild headache. Sitting at a 4:15pm lecture, I almost fell asleep.
Started again at 1am as usual. I was relatively conscious and aware throughout most of the program, which was probably the effect of the caffeine in the Coke & rum I had consumed 20 minutes before bedtime. Remind me not to get into that silly habit. I was probably still synchronised with the machine, I'm pretty sure I didn't lay down any memories during the delta segments. I didn't remember taking off the earphones, although I remember waking once or twice up after the program had finished. They were only brief periods of partial consciousness though, nothing which would have caused what I experienced next.
I slept in until 10 hours after the start of the program! I woke up several times before that, maybe at 8 hours, but fell back to sleep. I think I was dreaming for most of this 2 hour period. This is not unusual behaviour for when I've been sleep-deprived for the previous few days (say, 6.5 hours per night), but it would certainly be unusual in the context of a good night's sleep for the previous few days.
I'm thus led to the following hypothesis:
This is just a hypothesis, it's speculation derived from the evidence above. Much more evidence would be needed before I could form any solid conclusion. But based on this evidence alone, I can't recommend using brainwave synchronisation as the primary means for treating insomnia. It may be good for occasional use, in addition to other measures.
If you suffer insomnia, please consider reading up about it in the conventional medical literature if you haven't already done so. Here's some links to help you get started: