General Applications
In general, acceptable sound levels are based on sound level intensity and duration of exposure. We surveyed the recommendations from the agencies listed below, and at the time of writing this article the sound limits varied between 70-75 dBA for a 24-hour period and 85-90 dBA for a 8-hour period. At a practical level, if you work environment is noisy (e.g., construction site, factory, etc.) the 24-hour recommendation might be more relevant, while if you work in a quiet environment (e.g., office, library, etc.) the 8-hour recommendation. Please note that these are only general guidelines, and also these organizations may change their recommendations over time as well.
- World Health Organization
- US Department of Labor (Occupational Safety and Health Administration)
- Center of Disease and Control (National Institute of Occupational Safety and Health)
- Environmental Protection Agency
- Canadian Centre for Occupational Health & Safety
Nursery Applications
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.