WASHINGTON (AP) — From the cacophony of day care to the buzz of TV and electronic toys, noise is more distracting to a child's brain than an adult's, and new research shows that noise can hinder how youngsters learn.

In fact, one of the worst offenders when a tot is trying to listen is other voices babbling in the background, researchers said at a meeting of the American Association for the Advancement of Science.

"What a child hears in a noisy environment is not what an adult hears," said Dr. Lori Leibold of Boys Town National Research Hospital.

That's a Catch-22 in our increasingly noisy lives because "young children learn language from hearing it," said Dr. Rochelle Newman of the University of Maryland. "They have a greater need for understanding speech around them, but at the same time, they're less equipped to deal with it."

It's not their ability to hear. For healthy children, the auditory system is pretty well developed by a few months of age.

Consider how hard it is to carry on a conversation in a noisy restaurant. Researchers simulated that background in a series of experiments by playing recordings of people reading and talking while testing how easily children detected words they knew, such as "playground," when a new voice broke through the hubbub, or how easily they learned new words.

The youngest children could recognize one person's speech amid multiple talkers, but only at relatively soft noise levels, Newman said. Even the background noise during relatively quiet day care story time can be enough for tots to miss parts of what's read, she said.

It's not just a concern for toddlers and preschoolers. The ability to understand and process speech against competing background noise doesn't mature until adolescence, Leibold said.

Nor is the challenge just to tune out the background buzz. Brief sudden noises — someone coughs, a car horn blares — can drown out part of a word or sentence. An adult's experienced brain automatically substitutes a logical choice, often well enough that the person doesn't notice, Newman said.

"Young children don't do this. Their brain doesn't fill in the gaps," she said.

Children who were born prematurely may have an additional risk.

When preemies spend a long time in an incubator, their brains get used to the constant "white noise" of the machine's fan — different from a full-term baby who develops hearing mom's voice in the womb and thus is wired to pay more attention to voices, said Dr. Amir Lahav of Harvard Medical School.

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