My Calm Mix

Why calming sounds work

A short, honest look at the research on noise, nature sounds and sleep. What has been shown, and what has not.

1. Steady sound hides sudden noise

We are rarely woken by noise itself, but by changes in noise: a door, a car, a voice. A steady background sound makes those peaks stand out less. This is called sound masking.

In a small sleep-lab study, healthy volunteers slept with recorded intensive-care-unit noise. Arousals rose from 13.3 per hour at baseline to 48.4 per hour with the noise, and fell back to 15.7 per hour when white noise was added. The authors explain this by the smaller gap between background and peak noise. Only a handful of people took part, so it is a hint rather than proof.

An older randomised study with 40 newborns (2 to 7 days old) found that 80% fell asleep within five minutes with white noise, against 25% without it.

2. Pink noise and deep sleep

Pink noise sounds softer than white noise: it has less energy in the high frequencies, a bit like steady rain. Researchers use it in sleep experiments.

In a 2013 study, short sounds played in time with the brain's slow waves during deep sleep strengthened those waves and improved memory consolidation overnight. Sounds played out of time had no effect. A 2017 study in adults aged 60 to 84 used pulses of pink noise in the same way; the memory gain was linked to the increase in slow-wave activity during stimulation.

These studies used carefully timed sound pulses, not a constant background. Continuous pink noise from an app is not the same thing.

3. Nature sounds and stress

Natural sounds such as water, wind and birdsong are often described as restorative. A 2021 review in PNAS pooled the results of 18 studies and found that natural sounds were linked to lower stress and annoyance and to better health and mood.

In a 2017 brain-imaging study, listening to natural sounds rather than artificial ones shifted brain connectivity and increased heart rate variability linked to the body's rest system. In another study with 40 people, recovery after a stressful task tended to be faster with nature sounds than with traffic-type noise.

4. What we do not know

A 2021 systematic review of 38 studies rated the quality of evidence that continuous noise improves sleep as very low. It also warns that noise can harm sleep and hearing when it is too loud. Many people simply find these sounds pleasant, and that is reason enough to use them.

Listening safely

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Sources

  1. Stanchina ML et al. (2005). The influence of white noise on sleep in subjects exposed to ICU noise. Sleep Medicine 6(5):423–428. PubMed
  2. Spencer JA, Moran DJ, Lee A, Talbert D (1990). White noise and sleep induction. Archives of Disease in Childhood 65(1):135–137. PubMed
  3. Ngo HV, Martinetz T, Born J, Mölle M (2013). Auditory closed-loop stimulation of the sleep slow oscillation enhances memory. Neuron 78(3):545–553. PubMed
  4. Papalambros NA et al. (2017). Acoustic enhancement of sleep slow oscillations and concomitant memory improvement in older adults. Frontiers in Human Neuroscience 11:109. PubMed
  5. Buxton RT et al. (2021). A synthesis of health benefits of natural sounds and their distribution in national parks. PNAS 118(14):e2013097118. PubMed
  6. Gould van Praag CD et al. (2017). Mind-wandering and alterations to default mode network connectivity when listening to naturalistic versus artificial sounds. Scientific Reports 7:45273. PubMed
  7. Alvarsson JJ, Wiens S, Nilsson ME (2010). Stress recovery during exposure to nature sound and environmental noise. Int J Environ Res Public Health 7(3):1036–1046. PubMed
  8. Riedy SM, Smith MG, Rocha S, Basner M (2021). Noise as a sleep aid: a systematic review. Sleep Medicine Reviews 55:101385. PubMed
  9. Hugh SC et al. (2014). Infant sleep machines and hazardous sound pressure levels. Pediatrics 133(4):677–681. PubMed

This page is general information, not medical advice.