This is the long sheet the shorter notes hang off. Each section below is summarised here and written out in full in Notes; the free bedtime calculator handles the other half of the problem, which is when to be asleep rather than what to hear.
Pick your sound: the colours of noise
White, pink and brown are real acoustics rather than marketing. Each describes how a sound's energy is spread across frequencies, and the practical difference is texture. White spreads energy evenly and reads as a bright, full-spectrum hiss. Pink tilts it downward and lands somewhere near steady rain. Brown — properly Brownian, named for the random walk rather than the colour — tilts down further still into a low rumble with almost no hiss in it.
Most people find white harsh at the volume masking actually needs, and find brown the easiest to live under for a full night. Pink sits between them, which is roughly why rain is the most-loved sleep sound there is. Give each one a whole night rather than a five-minute audition: the question is not whether it sounds pleasant, it is whether you notice it at three in the morning.
The evidence, read honestly
Studies of noise as a direct sleep enhancer are small, methodologically varied, and mixed in their conclusions; some flag possible costs to sleep depth. Nothing in that literature supports "scientifically proven deeper sleep" as a blanket claim, and a sales page that says otherwise is reading press releases rather than papers.
What is well founded is duller and more useful: masking. What wakes you at night is rarely steady loudness, it is change — the door, the siren, the shower upstairs at two in the morning landing on a silent room. Steady sound raises the floor so those spikes arrive as small changes instead of alarms. If you sleep beside thin walls, a snoring partner or a city street, that is acoustics, not placebo.
All night, or a timer?
Both work, and the failure mode belongs to neither: it is the timer that hard-stops. Sudden silence can pull you up an hour later as surely as a sudden noise, which is why a fade measured in minutes is worth more than any extra sound in a library.
If your room gets noisy overnight, play all night at a modest level. If you only need help crossing from awake to asleep, fade out — and if you get up in the small hours, start it again when you come back; the sound is a cue as well as a mask.
How loud is right
Under the level of a quiet conversation. Masking works by raising the floor of a room, not by out-shouting what is in it — if you would have to raise your voice over the sound, it is too loud to spend eight hours inside. Fix a persistent noise problem with the darkest texture that works at a comfortable volume, never with the loudest volume of a bright one.
The three in the morning problem
Surfacing briefly between sleep cycles is normal architecture, not broken sleep. The trouble is the ninety seconds afterwards: the clock, the arithmetic about how much is left, the phone. Turn the clock to the wall, leave the phone alone, and if you are clearly awake after fifteen or twenty minutes, get up in dim light and do something dull until you are sleepy — that is stimulus control, borrowed from CBT-I, and it works by breaking the association between the bed and lying awake in it.
What it should cost
A subscription is an honest price for something with an ongoing cost behind it. A streamed catalogue has one: hosting and delivery, every night, for everybody. That is a real bill and passing it on is fair.
Sound that is synthesized on your own phone has no such bill. Nothing is stored at our end and nothing is served, so once the app is installed it costs us nothing at all to keep working — which is why Hush is one payment of $19.99 rather than a yearly one. It is the architecture that sets the price, not a promotion.
The short answers
- Which noise is best? None of them is proven better. Pick by texture, and judge it over a whole night.
- All night or a timer? Either — as long as the timer fades rather than cuts.
- How loud? Under a quiet conversation, for the whole night.
- Does it treat insomnia? No. It masks sound. Chronic insomnia is treated with CBT-I, by a clinician.
- Why is Hush not a subscription? Because there is no server behind it to pay for.