What scientific research records about sleep sounds

Sleep sounds are widely used at bedtime, ranging from natural audio recordings to continuous broadband noise. Controlled research examines how these auditory stimuli affect sleeping physiology, awakening thresholds and waking recovery.

Categories of night audio and broadband noise

A 2022 review of sounds tested for inducing sleep sorted them into three kinds: coloured noises such as white and pink noise, sounds associated with autonomous sensory meridian response such as rain or burning firewood, and music ^[9]. Covering 19 studies, including 8 on coloured noise, 3 on ASMR-type sounds and 8 on music, it noted that devices and apps widely use such sounds although the effect has not been validated ^[9].

Broadband noise has shown inconsistent findings. A systematic review of 38 articles on continuous white or similar broadband noise and sleep found results at both extremes, from reported improvements to disrupted rest, which authors suggested stems from variations in noise profiles, measurement methods and controls ^[1]. Under GRADE criteria, the evidence that continuous noise benefits sleep was rated as very low, with warnings that it may negatively affect sleep and hearing ^[1].

Laboratory findings on pink noise and awakenings

In a seven-night laboratory study with polysomnography in 25 healthy adults, intermittent environmental noise (93 events peaking at 45 to 65 dBA) reduced deep N3 sleep, while continuous pink noise played on its own at 50 dBA reduced REM sleep compared with a quiet night ^[2]. Pink noise at 40 dBA was evaluated only alongside noise events ^[2]. Adding pink noise to noise events worsened sleep structure despite minor reductions in fragmentation, and earplugs offset nearly all noise effects until 65 dBA ^[2]. Subjective ratings of sleep, alertness and mood worsened after noise events with or without pink noise, while pink noise alone matched the quiet night ^[2]. Morning cognition, cardiovascular measures and hearing showed no change ^[2].

CIBDOL · Laboratory findings on pink noise and awakenings

Disruption patterns depend on sound types. In a sound-attenuated laboratory with 12 healthy volunteers exposed to 14 hospital sounds at 40 to 70 dBA, electronic sounds caused more EEG arousals than voices, arousals were less frequent in N3 than N2, and in REM sleep arousal probability varied less while heart rate rose higher and longer ^[3]. In a systematic review of 74 field studies, pooled polysomnography showed the unadjusted odds of awakening rose by roughly 35 percent per 10 dBA increase in indoor traffic noise ^[4]. Evidence was rated moderate for traffic-induced cortical awakenings, low for movement-based disturbance, and very low for other noise outcomes ^[4].

Nature recordings evaluated during waking hours

Research on natural soundscapes has predominantly observed awake participants. In a 2010 experiment with 40 awake participants exposed to sounds after stressful arithmetic, skin conductance recovered faster during nature sounds than during noise, while heart rate variability showed no effect; sleep was not measured ^[5]. Similarly, two 2025 laboratory experiments involving 100 and 30 participants found that 30 minutes of recorded forest sounds scored higher for mood, restoration and cognition than urban sounds, but cardiovascular, cortisol and immune markers did not differ, and sleep was not measured ^[6].

Clinical trials and limitations of bedtime audio

Studies evaluating nature sounds in sleep settings remain limited. In a four-night crossover trial with 68 intensive care patients in India, earplugs and eye masks outperformed ocean recordings on questionnaire sleep scores ^[7]. In a trial with 60 shift workers in Thailand, combining water sounds at 20 to 30 decibels with lavender fragrance did not significantly differ from fragrance alone for total sleep (p = 0.454) or deep sleep on wrist devices, and water sound was never tested alone ^[8]. No polysomnography study was found in which recorded nature or rain sounds alone were played to healthy adults during sleep; the nature-sound studies the search returned that assessed sleep did so in patients, by questionnaire, without a control group, or with the sound combined with another stimulus ^[7][8].

A 2025 perspective on audio sleep tools highlighted that evidence for ambient noise remains inconclusive, noting an absence of robust randomised controlled trials and questioning how bedtime app use aligns with screen-reduction advice ^[10]. This review reports experimental findings without endorsing products, playlists or sleep practices; individuals experiencing persistent sleep difficulties should speak to a doctor.