All mommas want more sleep, and you may have heard that introducing white noise will help baby fall asleep faster and sleep longer. Sounds like baby magic, but does it really work? The short answer: yes, but don't make the noise too loud.
Let's explore the data. A small trial in 1990 demonstrated the babies exposed to white noise fall asleep faster (Spencer et al., 1990). Additionally, a recent 2017 study found that playing white noise "significantly decreased the daily crying durations and increased the sleeping durations of colicky babies". However, a concerning 2014 study demonstrated that white noise machines played at the max level are capable of producing sounds "damaging to infant hearing and auditory development" (Hugh et al., 2014). It is therefore very important to make sure that white noise is played at an appropriate level.
So what noise level is best for babies' sleep? Here, we encounter some controversy. The 2017 study of colicky babies set white noise levels to 55 dB. However, the 2014 study on white noise hazards recommends not exceeding 50 dB. Pediatrician Dr. Harvey Karp, author of Happiest Baby on the Block, says, "Sound doesn’t start boosting sleep until it gets to 60 to 65 dB" (Karp). As babies experience 72 to 88 dB while in the womb (Smith et al., 1990), the 55 to 65 dB range (the loudness of a shower) seems reasonable. Using a free, easy-to-use decibel meter app (such as Decibel Meter) will allow you to set your noise machine at the correct level. For the Hatch Rest sound machine, the wave setting at 30% provides 60 dB of noise when placed 2 feet from baby's sleep space.
Sources:
Spencer JA, Moran DJ, Lee A, Talbert D. White noise and sleep induction. Arch Dis Child. 1990;65(1):135-137.
Hugh SC, Wolter NE, Propst EJ, Gordon KA, Cushing SL, Papsin BC. Infant sleep machines and hazardous sound pressure levels. Pediatrics. 2014 Apr;133(4):677-81.
Karp, H, "Is White Noise Bad for Babies' Hearing?", Happiest Baby, accessed 25 March 2021, <https://www.happiestbaby.com/blogs/baby/is-white-noise-bad-for-babies>.
Smith CV, Satt B, Phelan JP, Paul RH. Intrauterine sound levels: intrapartum assessment with an intrauterine microphone. Am J Perinatol. 1990 Oct;7(4):312-5.