Efficacy of pink noise and earplugs for mitigating the effects of intermittent environmental noise exposure on sleep

STUDY OBJECTIVES: Nighttime environmental noise (EN) exposure disturbs sleep and increases morbidity and mortality. Affordable and effective countermeasures are needed, but rigorous research is scarce. This study investigates the efficacy of pink noise (PN) and earplugs for mitigating the effects of intermittent EN on sleep. METHODS: Twenty-five healthy adults (mean ± SD age 28.5 ± 5.9 years, seven male) participated in a seven-night polysomnographic laboratory study with different noise conditions including exposure to EN (93 events; maximum sound pressure level 45 to 65 dBA), PN (40 or 50 dBA), earplugs, and their combination. In the morning, participants completed cognitive tests, cardiovascular measurements, hearing tests, and surveys. RESULTS: Compared to a noise-free control night, EN reduced N3 deep sleep (p < .0001) while PN reduced REM sleep (p < .001). Adding PN to EN worsened sleep structure, despite minor dose-dependent improvements of EN-induced sleep fragmentation and N3 sleep increases. Earplugs mitigated nearly all EN effects on sleep but started failing at the highest EN level (65 dBA). Morning cognition, cardiovascular measures, and hearing were not affected by nighttime noise, but subjective assessments of sleep, alertness and mood were significantly worse after EN and PN exposure. CONCLUSIONS: In contrast to PN, earplugs proved efficacious in mitigating the effects of EN on sleep. Considering the importance of REM sleep for memory, emotion regulation, and neurodevelopment, the negative effects of PN on REM sleep caution against the widespread and indiscriminate use of broadband noise (BN). Additional research on optimal BN color/level and long-term use is needed, especially in vulnerable populations. CLINICAL TRIAL REGISTRATION: Registered at clinicaltrials.gov under "Broadband Sound and Sleep"; https://clinicaltrials.gov/study/NCT05774977; registration # NCT05774977.