What can your baby hear -- and how much does she understand? Learn all about what's going on between those cute little ears.

You aren't just talking to yourself when you read Goodnight Moon aloud to your newborn. Although she may not seem to be paying attention, she's taking in every word. In fact, she's been a good listener since before she was born. By the 28th week in utero, her ears were already fully developed and functional. Now, nestled in your arms, your child can probably hear things as well as you do.

That's good news, because those two little ears have a big task to accomplish, relaying countless sounds to help your baby learn about the world. By the end of this year, she'll have grasped the basics of language and may even be able to say a few words! Learn how to help this process along, and keep your child's precious hearing safe for decades to come.

Testing, Testing

It's often hard to tell whether your baby can hear you -- after all, he isn't old enough to say, "Read you loud and clear!" Luckily, about 70 percent of infants get their ears checked before they leave the hospital. Ask whether your child was screened, and if he wasn't, schedule a hearing evaluation within the first month, advises Diane Sabo, Ph.D., director of audiology at Children's Hospital of Pittsburgh.

If your baby passes the test, then he's hearing the noises around him, even if he doesn't seem very responsive. There's an explanation for this: "At birth, sound is carried from the auditory nerve to the brain, but the brain doesn't know what to do with the information yet," says Brad Stach, Ph.D., president of the American Academy of Audiology and head of the Division of Audiology at Henry Ford Health System, in Detroit. But your child's eager mind won't stay clueless for long. The brain immediately starts to form mechanisms to locate where a sound is coming from, and it begins to learn to associate the sound with meaning.

As weeks pass and his central nervous system and motor skills develop, your baby will start to respond to routine sounds. Your voice, of course, is one of the most familiar of all -- he may kick, smile, or become calm when you talk or sing to him. And though you may feel silly about making high-pitched "baby talk," don't: "Moms and dads seem hardwired to speak in parentese," says Charlotte Johnson, Ph.D., a speech pathologist at Children's Hospital of Pittsburgh. And, she says, infants seem to be particularly stimulated by it as well.

The Sounds of Progress

Though some experts estimate that a child learns up to 90 percent of her speech and language from just listening to the world around her stroller, there's plenty you can do to stimulate your baby's auditory system.

  • Read, sing, and talk to your baby as much as possible. Give brief, simple running commentaries of what you're doing ("Mommy is putting rice in a bowl for you")
  • When your child is looking at something, tell him as much as you can about it: "That cat is a baby, so we call her a kitten."
  • Imitate the sounds that various objects make -- when you see a car, say, "Vroom!"
  • Play music at a moderate volume, or make your own with real or homemade instruments (a pot and spoon make a neat drum set).
  • Introduce age-appropriate toys with sound components. A farm-animal busy box, for instance, with cows that moo and horses that neigh with the push of a button, is a great choice. Or try a doll that sings a song if you squeeze her hand. "It teaches babies that sound doesn't just happen," Dr. Sabo says.

What's Normal?

Here are some typical hearing milestones to keep an eye (and ear) out for.

  • By 3 months: Your baby will be startled by loud, sudden noises and will wake or cry out in her sleep if someone disturbs the quiet.
  • By 6 months: If he hears a loud noise, he'll turn to look for its source, and he can recognize his name. He'll start babbling, chuckling, squealing, and blowing raspberries -- all of which are precursors to actual words.
  • By 12 months: Even soft sounds will cause your little one to turn her head, and her babble will sound more like language. She'll grasp the meaning of certain phrases (for instance, "Bye-bye!"), and she may even use simple words, like "Dada" and "Mama." When music plays, she'll bounce and try to sing.

If your baby doesn't exhibit these behaviors on schedule, talk to your pediatrician so she can decide whether to order further hearing tests. Early detection and intervention can help ensure that your little one doesn't miss out on this incredible time to learn.

Is There a Problem?

About two to three of every 1,000 babies in the U.S. are born with significant and permanent hearing loss. Still, if your child doesn't pass his initial hearing test, don't panic. Have him reevaluated in a few weeks. If there's concern after that, he'll need more testing and an assessment by an audiologist before he's 3 months old.

Even if your baby passes the test, tell your doctor if you suspect a problem at a later point. He'll probably check for an ear infection, a common culprit. Medical attention is important, because persistent ear infections can lead to long-standing mild hearing loss and can even damage the middle ear's bones. Some less-common causes of hearing loss, temporary and permanent, include head injuries, meningitis, German measles, severe jaundice, and a family history of permanent hearing loss in childhood.

Parents Magazine