I saw a TED talk about researchers playing pulsating pink noise while a test subject is in Stage 3 Non-REM / Slow Wave / Deep sleep and observing an increase in Delta wave EEG activity. This seems to indicating that the burst frequency of the pink noise is matching the dominant frequency of the Delta waves. (Skip to 5:00 to hear a sample of the sound)
My question: While a spectral analysis shows a range of brain wave frequencies, and many sources define a range such as "0.5-4 Hz", I'd like to find a more precise dominant frequency of Delta waves.
The video inspired me to write my own small computer program to make my laptop play a similar pulsating pink noise pattern on the table next to my bed last night. I arbitrarily chose 1 Hz as the pulse frequency, and the following pattern:
30 min silent (to give me time to wind down and fall asleep) 60 min sound 33 min silent 54 min sound 40 min silent 45 min sound 49 min silent 37 min sound 57 min silent 30 min sound 30 min silent
So roughly 5x 90-minute sleep cycles with an increasing ratio of silence to noise to mimic the ratio of REM to NREM as the night progresses. I've read that REM is characterized by un-synchronized brain waves and NREM is where you see large amplitude synchronized Delta waves which the sound experiment is trying to help stimulate. Tonight I will wear my FitBit bracelet with heart rate and sleep stage tracking to see if the readings match the sound schedule.
- How credible is the hypothesis that playing sounds can affect the quality of sleep?
- Would a different sound than pulsating pink noise work better?
- Does the phase matter?
- Also, I couldn't help but notice that Deep NREM sleep seems to be the only time you see a single large amplitude frequency dominate on EEG and it's suspiciously close to the average Resting Heart Rate of 60 bpm...are Delta waves and heart rate related?