What your baby hears:
A baby's capacity to hear develops even before birth. Peering into the womb via ultrasound, scientists have observed fetuses reacting to loud noises at 24 weeks' gestation.
At birth, an infant is already able to recognize specific sounds. For example, nursing newborns will suck harder at the sound of their mother's voice, says Joanne Roberts, Ph.D., a hearing and language researcher at the Frank Porter Graham Child Development Center at the University of North Carolina, in Chapel Hill. And by around 4 months, a baby can localize sound -- that is, figure out where a noise is coming from.
The structure of the ear -- though fully developed -- is very delicate in infants, making them particularly sensitive to volume. Too much noise can actually cause ear damage, according to Lynn Luethke, a scientist at the National Institute of Deafness and Other Communications Disorders. Experts advise parents to shield their babies from very loud noises and to give them some silent time each day away from TVs, telephones, and noisy siblings.
Boosting your baby's skills:
Talk, read, and sing to your baby. "The sound of adult voices helps prime a baby's brain, making her more receptive to learning language skills later in life," says Karen DeBord, Ph.D., a child-development specialist for the North Carolina Cooperative Extension Service. Studies have found, for instance, that hearing the rhythm of the spoken word helps children learn to read when they get to school. "It doesn't matter that your baby can't yet understand what you say," Dr. DeBord says. "She'll learn the patterns and rhythms of her native language."