Oh we can just throw this shit right out. 13 participants? 60 and older in the US?
How about some controls for Diet, Exercise, and other general, you know, basic science shit? No? Well then allow me to just go ahead and call this study "statistically insignificant to the point of being potentially misleading" because I have pretty high expectations when it comes to rigor in academic study. This is what Northwestern chooses to highlight?
Point being, I grew up sleeping with Bach, John Jarvis, and Yngwie Malmsteen music for 20+ years. I think shoving a few cutesy-noise waves into the ears during rest is probably nice, like having a good pillow or decent sheets, but otherwise highly over-stated. This 13 person old fogey study means jack-shit in the big picture.
Want to have some real fun?
Let's get the Neural Network "Music" that Google is Researching to play during the sleep of 60 year olds and find out how that goes over. All these tech-approaches to very primal emotional pathways are disturbing to be on a general principle, mostly because not a single one of them has shown anything other than Placebo-esque results, and when placed against a control group, fail. Bonus hypothesis: The Google Machine Learning Music actually drives the Elderly Insane.