What you'll get from this post
- The difference between white, pink and brown noise, in one number
- A simple way to find your focus noise: hide what you're hearing, match the loudness, sneak in repeats
- A result that surprised me: my likes were decided by my body, not my mood
Here's the answer first: the sound that helped me focus most was not brown noise. It was a much darker noise that doesn't have a name. I found it by listening to 50 versions of "shhhh" with my eyes closed, under a staircase at Hong Kong airport.
A night under the stairs
I couldn't fly home that night. I found a spot under a staircase in Terminal 2 where I could lie down. I'd taken my medication, my head was wide awake, and there was nothing to do. So I decided to focus on something.
I put on my usual "brown noise 10 hours" video. I have ADHD tendencies, and this hiss is a focus tool for me. Then a question hit me: who decided what this sound should be?
"Brown" isn't a color
Noise colors come from light. Mix every color and light looks white; mix every pitch at equal strength and you get white noise. More low pitches is closer to red light, so pink. More high pitches, blue.
Brown is different. It's named after the botanist Robert Brown and Brownian motion: a random walk. Add up white noise step by step and you get the trail of a random walk. Low pitches stay loud. Every time the pitch doubles, the level drops by 6 dB. That's brown noise.
That −6 comes from how the noise is made. Nobody chose it for focus. So I was free to change it.
Knobs, and a rabbit hole
With an AI, I built a page where I could rebuild the noise with seven knobs: slope (how fast the highs fade), a cutoff, left/right same or different, wobble, a beat between the ears, slow swells, and occasional grains.
Every knob turned it into a different sound: a propeller plane, rain from above, a sparkler crackling. Fun, but useless. I was choosing by mood.
Doubting my own taste
So I made it an experiment.
- Hide the recipe. Each sound only had a number.
- Close my eyes. The page read the number aloud; I answered by voice.
- Repeat some sounds secretly, to see if my answers were stable.
- Match the loudness of all 50 with the broadcast standard (LUFS). In my first round, my favorite turned out to be simply the quietest one.
50 blind sounds
39 new combinations spread evenly, 7 earlier favorites, and 4 secret repeats. I rated each from 1 to 5.
My answers were stable: of the 4 repeated pairs, 3 got the exact same score, and the average gap was 0.25 points.
And at number 41, I said out loud: "This is it."
What number 41 is
- Slope: −13.3 dB per octave (more than twice as steep as brown)
- Cutoff: everything above 420 Hz trimmed further
- Left and right: the same
- No wobble, no beat, no grains
Very heavy, very dark, no decoration. At 1 kHz it's about 41 dB quieter than brown noise, roughly 1/10,000 of the power. Noise darker than brown is sometimes called black noise (there's no agreed definition).
One more thing: #41 was not the sound I had saved as a favorite the night before. It was a new one with a similar recipe. Blind, I felt "this is the one I liked before", and I scored it higher. My taste was reacting to the sound itself, not to a memory.
It was the body, not the mind
I expected to pick "calming" sounds. The data said otherwise.
- The sounds I liked were the ones where I felt absorbed and my body felt good
- The ones I disliked made my body uncomfortable, felt crackly, and tired me out
- "Calm" or "restless" had almost nothing to do with what I liked
Sound as a fluid
With my eyes closed, the sounds moved. "Dots flowing left to right." "A spinning propeller." "Deep, like the sea, going straight down." Matching these to the knobs: a left/right difference sounded like flowing, fast wobble like spinning, and nothing at all on the sides sounded deep. That deep one was my favorite.
What I still don't know
This was one person, on one tired night. I don't know yet whether #41 still wins on a fresh morning, whether it actually makes my work faster, or whether anyone else would feel the same.
Next
I'll listen again, outside and on a quiet morning, and count how much I get done with each sound.
Want to find your own sound? The listening page I used can be opened as-is. Leave a comment if you'd like to try.
Where does your focus noise sit: white, pink, brown, or somewhere without a name?
A self-experiment by one person. Not medical advice. Keep the volume low when listening for long periods.
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