Seven things researchers have tried to wake sleepers with, ranked by evidence
From a 520 Hz tone to a puff of peppermint, seven ways researchers have tried to rouse deep sleepers, ranked by how many sleepers were tested and what happened.
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Twenty-three of 24 children woke to a recording of their mother’s voice. Only 14 woke to a standard alarm tone. That was the result of a 2006 trial by Smith and colleagues at Nationwide Children’s Hospital in Columbus, Ohio, published in Pediatrics, and the children had been in deep sleep when each signal played at the same 100 decibels.
You probably assume the loudest or most annoying sound wins. Researchers have been testing that assumption for decades, mostly because of fire deaths, and DontSnooze (an iPhone app that wants a video from you seconds after the alarm) only exists because waking up and staying up are separate problems. The ranking below uses three questions. How many sleepers were tested? Were they in deep sleep? Did anyone repeat it?
1. A low, harsh tone beats a high, pretty one
The best-tested waker is a sound, and the surprise is its shape. Most smoke alarms beep near 3,100 Hz. The best performer in the lab is a square wave near 520 Hz, the buzzy, flat-sounding tone you would never choose as a ringtone. At 75 dBA it woke over 90 percent of two groups of deep sleepers in a 2008 paper by Thomas and Bruck at Victoria University in Melbourne: young adults at a blood alcohol level of 0.05, and adults with hearing loss. A louder version woke every one of them.
Dorothy Bruck’s group then compared nine signals on 39 young adults over three nights. The 400 Hz and 520 Hz square waves had the lowest waking thresholds of the lot (Bruck, Ball, Thomas and Rouillard, Journal of Sleep Research, 2009), so pitch and waveform both matter. If you want the full trial-by-trial account, the post on what fire-safety research found lays it out.
2. A familiar voice comes second
Back to the Columbus children. Nine of them woke to the voice and not the tone, and none woke to the tone alone. Eighty-three percent of the voice group completed a simulated escape within five minutes, against 38 percent of the tone group. You can try a version of this at home: a recording of someone you trust saying something short is harder for a sleeping brain to ignore than a beep, which is the same reason your own name cuts through a noisy room.
The catch is the sample. Twenty-four kids is small, and one mother’s voice says little about a stranger’s. The 2018 follow-up with 176 children is why voice still holds second place instead of dropping.
3. A shaker under the pillow works for most, but not all
If a sound can’t reach you, touch is the oldest alternative. The Victoria University team tested bed and pillow shakers on 38 adults aged 18 to 80 with hearing loss. Most woke, with roughly 17 to 20 percent sleeping through at the strength a shaker ships with. Among young adults at 0.05 blood alcohol, the miss rate was higher, 36 to 42 percent. The 520 Hz tone beat the shakers in both groups.
Think about that before you buy a vibrating pillow pad for a heavy sleeper. It is better than silence and worse than a good tone. This guide to alarms for deaf and hard-of-hearing sleepers covers what is actually on sale.
4. Expecting a wake-up time starts the hormones early
This one does not wake anyone, and it still belongs on the list. If you have ever surfaced a minute before your alarm, you may have met it. In a 1999 Nature paper, Jan Born and colleagues at the University of Lübeck reported that sleepers told to expect waking at a set time showed a marked rise in the hormone ACTH about an hour beforehand.
Your body, in other words, can prepare for the end of sleep. The paper does not show it can wake someone who would otherwise stay down, and the evidence is a hormone level, not a wake-up. That is why it ranks fourth.
5. Light is a poor waker and a decent finisher
Try this thought experiment: a bright flashing light in your bedroom. It sounds like it should work. In the Victoria University trials, a strobe above the intensity the safety standard requires woke only 27 percent of the hard-of-hearing adults, and roughly three quarters of both test groups slept through it. As a waking signal it did badly.
As a way to feel better afterward, light does more. A 30-minute artificial dawn lowered sleepiness in 16 people who reported trouble getting up (van de Werken, Giménez and colleagues, Journal of Sleep Research, 2010). Whether a sunrise lamp is worth the price is picked apart in this close reading of the sunrise alarm trials.
6. Smell barely registers once you are asleep
A scent alarm sounds charming, and it has been tested. Mary Carskadon and Rachel Herz at Brown University (Sleep, 2004) gave peppermint and pyridine, a foul-smelling coal-tar chemical, to six volunteers aged 20 to 25. Peppermint was ineffective in stages 2, 4 and REM sleep. Pyridine drew only sporadic responses and woke nobody in the deepest stage. When the smells failed, a tone woke the sleepers nearly every time.
The paper’s title says it plainly: odor alarms will not work for humans. So if you are thinking of waking tomorrow to a coffee machine’s aroma, expect the sound of it grinding to do the work.
7. Temperature has the least evidence of all
You know a hot room ruins sleep and a cool one helps. That is a different question from whether a change in temperature will wake you. No human trial we found measures how much warming or cooling it takes to rouse someone from a given sleep stage. Anything you read about a warming mattress pad or cooling blanket waking people on cue borrows from sleep-onset research, which is a different problem. It sits last, with a question mark, until someone runs the trial.
FAQ
What sound is best for waking a sleeping child?
A parent’s voice beat the standard tone in both trials from Nationwide Children’s Hospital. In the 2018 Journal of Pediatrics trial by Smith, Chounthirath and Splaingard, 176 children aged 5 to 12 were tested: the high-pitched tone woke 53 percent, while voice alarms woke 86 to 91 percent. Adding the child’s own name did not improve the result. The tone still wakes adults, who can then carry the child out.
Can a smell wake you from sleep?
Almost never. Stuck and colleagues (2007) tested five healthy volunteers and found that even the strongest purely olfactory stimulus did not raise the number of arousals. Carbon dioxide, which stings the nose through the trigeminal nerve rather than registering as a smell, did cause more arousals as the concentration went up.
Do smoke alarms wake sleeping people?
Often, but not for everyone. A 2007 Victoria University report found that the standard high-pitched alarm tone failed to wake roughly 4 in 10 adults with mild to moderately severe hearing loss. Sleepers who are intoxicated, sleep deprived or very young are also harder to rouse, and the Victoria University trials were designed around those groups.