# Sound: what the research actually says

Noise fragments sleep at levels far below what wakes you up, which is why the target is a number, not a feeling.



## All studies

- **Noise as a sleep aid: a systematic review** — Riedy SM, Smith MG, Rocha S, Basner M (2021), Sleep Medicine Reviews 55:101385. Evidence for white/pink noise as a sleep aid is weak and low quality — it can mask inconsistent sounds, but keep it quiet.

- **Auditory and non-auditory effects of noise on health** — Basner M, Babisch W, Davis A, et al. (2014), Lancet 383(9925):1325–1332. Night-time noise fragments sleep and raises cardiovascular risk even when people don't consciously wake.

- **Environmental noise and sleep disturbances: a threat to health?** — Halperin D (2014), Sleep Science 7(4):209–212. Review linking traffic and environmental noise with awakenings, sleep-stage changes and next-day effects.

- **Night noise guidelines for Europe** — World Health Organization Regional Office for Europe (2009), WHO. Recommends outdoor night noise below 40 dB (L_night) to protect health; effects begin around 30–35 dB indoors.

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Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.

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