Noise

What It Is

The sound in the room where you sleep.

Why It Matters

Noise fragments sleep, and you stop noticing it long before your body does. Sleep recordings made in people's own bedrooms, near airports and rail lines, show the odds of being pulled out of deeper sleep climbing steadily with each extra decibel of indoor peak noise, and the pattern is much the same whether the source is aircraft, road, or rail. Bedroom studies on two continents both found sleep efficiency measurably lower as bedside noise rose, with the decline appearing above roughly 46 decibels, and ordinary bedrooms already measure close to that line. The evidence is mostly measurement at home rather than trials, and the one randomized comparison of a quiet bedroom against a noisier one judged sleep by questionnaire alone.

What noise costs you is continuity rather than hours. Sound rouses the sleeping brain through arousals that fragment the night and trim deep sleep, while total sleep time does not move and may even drift up, which is why the damage hides from a bedtime tally. Your cortex stops reacting to a familiar noise long before your cardiovascular system does, and in a randomized trial, traffic noise peaking near 60 decibels in an otherwise quiet bedroom impaired blood vessel function the following morning. Your own sense of it is a poor guide too, since how much people say noise bothers them tracks neither what the microphones record nor how well they sleep.

Get the room quieter, and use earplugs when you cannot. In laboratory testing, nights that combined environmental noise with earplugs were indistinguishable from silent nights on nearly every measure of sleep structure and fragmentation, though the protection began to fail at the loudest events and nobody has tested comfort or adherence at home. Be wary of white and pink noise machines: pink noise did reduce arousals in that testing, but it cost REM sleep against a silent night without anyone noticing the difference, and layering it over environmental noise lost more than it gained; the trials reporting that white noise helps measured how hospital patients rated their sleep rather than how they slept. Both a window air conditioner and a fan measured louder rooms, so aim for a quiet room rather than a masked one, and expect a modest return that acts on the quality of your time in bed rather than its length.

• Basner, M., McGuire, S. (2018). WHO Environmental Noise Guidelines for the European Region: A Systematic Review on Environmental Noise and Effects on Sleep. International Journal of Environmental Research and Public Health. doi.org/10.3390/ijerph15030519
• Yamagami, Y. et al. (2023). Association between indoor noise level at night and objective/subjective sleep quality in the older population: a cross-sectional study of the HEIJO-KYO cohort. Sleep. doi.org/10.1093/sleep/zsac197
• Basner, M. et al. (2023). Associations of bedroom PM2.5, CO2, temperature, humidity, and noise with sleep: An observational actigraphy study. Sleep Health. doi.org/10.1016/j.sleh.2023.02.010
• Ding, Y. et al. (2025). Impact of white noise on sleep quality across age groups and in critically ill/non-critically ill patients: A systematic review and meta-analysis of randomized controlled trials. Sleep Medicine. doi.org/10.1016/j.sleep.2025.106869
• Basner, M. et al. (2026). Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep. Sleep. doi.org/10.1093/sleep/zsag001
• Hahad, O. et al. (2026). A randomized, double-blind, crossover study of acute low-level night-time road traffic noise: effects on vascular function, sleep, and proteomic signatures in healthy adults. Cardiovascular Research. doi.org/10.1093/cvr/cvag028