We fell down a weird rabbit hole this week about noise colors. Yes, noise has colors. And apparently the one everybody buys sleep machines for is not the best one for actually sleeping.
White noise is the hiss you get when every audible frequency plays at equal power. Think old TV static, or a box fan on high. It works for drowning out the neighbor's dog becuase it covers the full spectrum, but there's a catch in how we hear it. Human ears are way more sensitive to higher frequencies than lower ones. So when every frequency is equally loud, the high stuff dominates. That's why white noise can sound harsh or tinny after a while, and why some people wake up with a weird ringing feeling. It's doing its job. It's just doing it with a sharp elbow.
Pink noise plays the same full spectrum, but the power drops as the frequency goes up. Lower tones are louder, higher tones are softer, and the result sounds much more like something in nature. Steady rain on a roof. A waterfall from the next room over. Wind through trees. There have been a handful of small sleep studies (Northwestern did one that got passed around a lot a few years back) suggesting pink noise can help people spend more time in deep sleep and even nudge memory consolidation a bit. The samples were tiny, so we're not going to oversell it. But anecdotally, we switched our bedroom fan app from white to pink about a month ago and both of us noticed we stopped waking up at 3am for no reason.
Once you know pink exists, you find out the whole crayon box is in there. Brown noise (sometimes called red) drops the highs off even harder and sounds like a distant jet or heavy surf. A lot of people with ADHD swear by it for focus. Blue noise does the opposite, boosting the highs, and is mostly used in audio engineering for dithering. Violet noise is even more top-heavy and gets used in tinnitus therapy. Grey noise is tuned to sound equally loud across the spectrum to the human ear specifically, which is sort of the "correct" version of what white noise was trying to be. None of this is new science. Audio engineers have been naming these for decades. It just never made it to the Target shelf, where every sleep machine still proudly says WHITE NOISE on the box.
If you've got a favorite oddball fact we should chase down for next Friday, send it our way. We're always collecting them.
— Alexander & Amanda @ SBATC
