Acceptable sound levels for daily exposures vary by age, environment, and lifestyle, and in general are primarily governed by sound level intensity and duration. Recommendations by several health organizations are outlined below.
For hospital nurseries, it is generally recommended to keep continuous noise to volume levels below 50 dBA. However, the rationale for this limit has been based primarily on observations that introducing an intermittent stimulus above this level, in an otherwise quiet room, could disturb sleep, rather than being based on exposure limits for hearing safety (Refs 1-2). “Most knowledge about the damage to people from noise is from studies of persons with occupational exposures.” (Ref 3).
In general, we recommend 1) placing sound machines as far away from children as practical, 2) setting the volume as low as possible, and 3) limiting the duration of use.
Ref 1: Hugh, S. C., et al. “Infant Sleep Machines and Hazardous Sound Pressure Levels.” Pediatrics, vol. 133, no. 4, 2014, pp. 677–681., doi:10.1542/peds.2013-3617.
Ref 2: Philbin, M Kathleen, et al. “Recommended Permissible Noise Criteria for Occupied, Newly Constructed or Renovated Hospital Nurseries.” Journal of Perinatology, vol. 19, no. 8, 1999, pp. 559–563., doi:10.1038/sj.jp.7200279.
Ref 3: American Academy of Pediatrics Committee on Environmental Health. “Noise: A Hazard for the Fetus and Newborn.” Pediatrics, vol. 100, no. 4, 1997, pp. 724–727., doi:10.1542/peds.100.4.724.