A burst of "pink noise" may lead to more restorative sleep (news.mit.edu)

I think this is a great idea. I guess HN does think this scientific enough. ;)

From what I’ve read, a simple fan while sleeping checks the box for pink noise.

> You can make more of these electrical slow waves through an auditory stimulus, if it comes at just the right time.

I wonder: 50ms of pink noise at the right time to make your sleep more restorative. Why or how should such a “backdoor” have evolved? Sleeping by a crackling fire? Pure coincidence, like a bug in the system that never made enough of a difference to come under selection pressure?