Sound machines can be helpful tools to aid babies (particularly newborns) in falling asleep and staying asleep.  “Over nine months of pregnancy, babies get used to noisy and snug environments,” explains Dr. Dimitriu. “This is why babies like being swaddled, and also why babies like some gentle background sounds as opposed to complete silence.”  Around the age of three to four months, “the calming reflex will gradually disappear,” Karp says. “But by then, your infant will be aware of the connection between white noise and the pleasure of sleep.” So white noise machines can continue being helpful to parents.