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Photo of Peggy Nelson

Peggy Nelson, an associate professor at the University of Minnesota, links research with practice to improve children's learning in schools.

The sound of silence

U professor studies the effects of noise on classroom learning

By Emily Sohn

January 11, 2008

In an ideal world, classrooms are peaceful places where all students pay attention to the teacher, raise their hands to ask questions, and listen to each other's comments.

Few classrooms are like that, however, and it's not because rambunctious students are goofing off. Often, the room's construction is to blame. Or nearby traffic, outdated heating and air-conditioning units, and the scraping of chairs on hard floors. Add to that thin walls and ceilings, and you've got echo-filled classrooms that spell trouble for young learners, says Peggy Nelson, an associate professor at the University of Minnesota who specializes in audiology.

"In noisy rooms, kids make more noise," Nelson explains. "It's kind of a snowball [effect]," one that is especially problematic because hearing is an essential part of learning.

Nelson has spent her career studying the effects of both external and internal impairments to hearing on classroom learning. As she started diagnosing children with sensorineural hearing loss at the beginning of her career at Kansas State University about 25 years ago, she quickly realized that children who have difficulty hearing face unique learning challenges. "Hearing loss cuts you off from people and from incidental kinds of conversations," Nelson says. As a result, children with hearing loss don't pick up new vocabulary just by overhearing adults talk. And because they don't know what they are missing, they don't know what questions to ask--another kind of snowball effect.

What's more, children with hearing loss often have trouble behaving in social situations. And studies show that they're not as good at reading as other children. "It's a huge problem," Nelson says. On any given day, as many as 15 percent of school-age children, or more than a million U.S. elementary students, have trouble hearing, mostly from middle-ear problems or ear infections, according to the Centers for Disease Control and Prevention.

The link between troubled hearing and troubled learning is so strong that Nelson started to suspect that too many students were missing out at school. "In watching these kids even with slight amounts of hearing loss struggle with communication," Nelson says, "I wondered what happens in schools where communication isn't perfect."

In 1998, then at the University of Maryland, Nelson began measuring sound levels in empty urban, rural, and suburban classrooms around the country as part of a task force for the Acoustical Society of America. Some classrooms registered at a peaceful 30 decibels (dB), but others reached levels of more than 65 dB, about as loud as a roaring highway. "A teacher has to shout to be heard above that," Nelson says.

"In noisy rooms, kids make more noise," Nelson explains. "It's kind of a snowball [effect]."

Children with hearing loss aren't the only ones suffering from noisy classrooms, Nelson says. Even when their ears are fine, tests show that young children in particular have difficulty separating important sounds--like a teacher's voice--from background noise, such as a nearby highway. The human brain doesn't develop adult-like hearing skills, which enable more refined differentiation of sounds, until the mid-teenage years. Selecting and focusing on the right stimulus--the teacher's voice, for instance--just doesn't happen naturally for many children. Children with learning disabilities and speech difficulties especially have trouble learning in noisy situations, as do children with attention deficit disorders.

"They're in this swamp of sound and sight and tactile stimuli," says Daniel Shaw, U alum and speech language pathologist at Jefferson Community School in Minneapolis.

In 2001 Shaw called Nelson to see if she would help him gauge the impact of background noise on Jefferson's students. Many of the school's classrooms overlook a playground and busy Hennepin Avenue. As part of a series of experiments, the researchers presented second graders with lists of words that differed by just one sound, such as "ball" and "call," or "hot" and "heat." With no background noise, the young students performed well, Shaw says. Scores dropped when background noise was added, and students who spoke English as a second language took the biggest hit. More than half of Jefferson's students are native Spanish speakers, Shaw says, which means that a majority of children are struggling simply because they can't hear well enough.

Nelson's award-winning research has contributed to a growing body of evidence suggesting that quieter rooms may lead to better performance. When a major airport changed locations in Germany, Nelson says, students in schools near the new airport started scoring worse on vocabulary and reading tests. Students at schools near the old airport, on the other hand, started doing better when the airplane noise was gone.

Teachers also stand to benefit from acoustic adjustments. "Teachers are so used to vocal strain," says Shaw, that they're not even cued into the pain until it's gone. Three second-grade teachers who tested microphones realized quickly how much they'd been straining their voices, shouting to be heard above the din. Said one, "I don't believe how much better I feel after only one day."

Acoustic standards for tomorrow's classrooms

The latest standards, approved by the American National Standards Institute (ANSI) in 2002, recommend that the background noise in classrooms not exceed 35 dB, about as loud as a voice whispering from 15 feet away. While there are no laws yet to enforce these guidelines, a small but growing number of schools around the country, including some in the Twin Cities, are taking quiet seriously.

A perfect example is Burroughs Community school in south Minneapolis. As part of a major renovation in 2003, the elementary school added extra-quiet climate control systems, sloping ceilings that carry sound but not echoes, and angled walls that avoid the sound-bouncing effects of hard, parallel surfaces. Sound-absorbing ceiling tiles, well-insulated windows and doors, and thicker walls next to extra-loud spaces all dampen the carrying capacity of exuberant young voices in the building, which was also moved further away from a busy neighboring street.

With the ANSI guidelines in place, future schools can be made hearing-friendly at the blueprint stage, says Nelson. "Builders, planners, and architects have not thought of acoustics near the top of the list in the past. I hope it will become more of a priority," she says.