Any prolonged or very loud noise can damage hearing—and research has shown that some sound machines are too loud, especially for infants. As a result, it’s recommended sound be kept to 50 decibels around infants to prevent hearing issues. “Quieter is always a safer option,” Bates says.  Of course, if your baby is crying and can’t hear the sound machine, it’s okay to turn it up temporarily. “The sound needed to turn on the calming reflex when a baby is crying is a rough, rumbly noise that’s as loud as his crying,” explains Dr. Karp. But “Once your baby is calm, lower the level of your white noise to about the loudness of a shower”—or even less if you can get away with it.