“Pink Noise”, Memory, and Sleep

For the topic of sleep research, I chose to highlight and expand on a 2013 study showing a link between pink noise, memory, and sleep. (For the record: “Pink noise” sounds like radio or television fuzz, it is multiple octaves of frequency at a consistent volume)

The exact relationship between deep, “slow-wave” sleep and memory is still unclear but recent breakthroughs have underlined the two’s direct connection. A 2006 German study showed that “gentle electric current” can aid the brain falling into deep sleep, which improves sleep quality and increases overnight memory retention.[1] Now, researchers have shown the first evidence that “pink noise”, when calibrated to the EEG’s of the brain, can produce  similar effect. [2] Subjects who listened to synced “pink noise” had almost twice the memory retention as the control group, and longer periods of “deep sleep”. While this is initially promising, maybe it isn’t as exciting as it appears on the surface in terms of consumer applications. Both the electric current and pink noise strategies require subjects to be hooked into a device, which is not preferable. First, let’s look at the study:

 The Study’s Abstract: a small group of 11 subjects were asked to sleep two nights, one of the nights with no noise and one of the nights with pink noise played back responding to their brain waves (EEGs). In addition, they were asked a series of memory tests for remembering 100 words.

Results: The pink noise, when calibrated to the brain waves, both elongated the duration of “deep sleep” and magnified the size of the slow brain waves. Theoretically this should improve a subject’s memory, and that was shown to be the case. When the synced pink noise played, the subjects remembered an average of 22 words compared to 13 words, almost double the performance.

Implications: Sound stimulation has been tried before, mostly unsuccessfully. “White noise” –random noise like a fan or a fish tank– has been shown to reduce sleep disruption but not improve sleep. What makes this study different was that the noise was in sync with the subject’s brain waves. If the same “pink noise” is played at random, no effect can be seen.

Due to the necessity for live-syncing, electric current applications have arguably more consumer potency as things stand, since they do not have to be synced. Where Pink Noise might offer an advantage, however, would be the ability to take an average wave length pattern over a period of 7 or 10 days, and then to play the average pattern back for the following 30-45 days (just guessing numbers here). Since there appears to be no disadvantage for random pink noise, if the noise is sometimes out of sync it could act as a simple “white noise” that many people already use to subdue outside noises from pets or room-mates. When the Pink Noise is in sync it helps out, when it is not it’s not a big deal. In this strategy, consumers could not be forced to wear head-gear every night, but more research certainly has to be done on the issue.

[1] Nature.com: http://www.nature.com/nature/journal/v444/n7119/full/nature05278.html

[2] Closed-Loop “Pink Noise” and sleep: http://www.sciencedirect.com/science/article/pii/S0896627313002304