DozeClock › Guides
Guides
Plain-language answers to the questions behind the calculators — written from the same public data, with sources under every one.
White vs pink vs brown noise for sleep: what the colours mean and what the research foundWhite noise is flat and hissy, pink falls 3 dB per octave like steady rain, brown falls 6 dB like distant surf. The sleep studies are small and mixed; here is what they actually showed. · 5 minWhy am I still tired after 7 hours of sleep?Seven hours is inside the adult range, so the usual suspects are elsewhere: waking mid-cycle, a bedtime that drifts, caffeine that lingers, time in bed that is not time asleep. A checklist built from the numbers. · 5 minHow to use a sleep timer with sleep sounds (and why not to play them all night)Sound helps most while you are falling asleep; later it can wake you. How long to set the timer, what volume, which sounds to layer, and how it fits with the bedtime arithmetic. · 4 minWhat time should I go to bed to wake up at 5 am?9:15 pm for five cycles, 7:45 pm for six, 10:45 pm at minimum. A 5 am alarm is an early schedule; here is how to make it survivable — the bedtime, the evening, the caffeine line, and what to do about weekends. · 5 minHow long should a power nap be? What NASA, and a 10-vs-30-minute trial, foundTen to twenty-six minutes refreshes without grogginess; thirty or more risks waking from deep sleep. The numbers behind the advice, and how to time a nap so it does not cost you tonight. · 5 minSleep debt: is it real, and can you pay it back?Short nights add up, and the effects are measurable even when you feel fine. Weekend catch-up repays some of it and resets nothing. What the research supports and what it does not. · 5 minHow much sleep does a teenager need?8 to 10 hours a night for ages 14–17, according to both expert panels. Why most teenagers get less, what the biology of a later body clock means for school mornings, and how to turn 8 hours into a bedtime. · 5 minHow long does caffeine stay in your system?Half of it is still there about five hours later, a quarter after ten. The half-life ranges from 1.5 to 9.5 hours between people. What that means for a 3 pm coffee and an 11 pm bedtime. · 5 minHow long should it take to fall asleep?Ten to twenty minutes is normal for a healthy adult. Under five suggests you are short on sleep; over thirty, night after night, is worth attention. What the numbers mean and what to do at the twenty-minute mark. · 4 minThe 90-minute sleep cycle: rule or myth?Sleep does run in cycles and 90 minutes is a fair average, but a cycle can last 70 to 120 minutes. How to use the idea without obeying it. · 4 minWhat is the best time to sleep and wake up?There is no single best clock time; there is a best time for you, set by when you have to be up and by your chronotype. How to find it with the sleep-needs range, the cycle arithmetic and one rule about consistency. · 5 minCan't fall asleep after 20 minutes? What to do nextThe standard sleep-medicine move is to get out of bed. Why that works, what to do with the time, how sound can help, and when a slow night is just a slow night. · 5 min