New hearing test simulates noise of real world

University researcher Ruth Litovsky has developed a hearing test that simulates the noisy real world, and the results could improve our understanding not only of hearing but also of developmental and learning disabilities among children.

Everyday and everywhere, a cacophony of sounds compete for children’s attention. Because humans have binaural hearing — hearing with two ears — children usually can determine which sounds are more important: student chatter in the back of the classroom or the teacher’s lesson on multiplication, for example.

“Binaural hearing enables us to understand and engage in the world around us,” says Litovsky, a UW–Madison communicative disorders professor and an investigator at the Waisman Center, a facility devoted to advancing the knowledge of human development.

Without binaural hearing, different noises would blur together and become overwhelming. Thus, an impairment affecting binaural hearing could limit a child’s ability to pick out important sounds in noisy environments, which in turn could affect learning, speaking and, more generally, concentration.

Until now, no test effectively evaluated how well children can tune in some sounds and tune out others. “Most hearing tests that are available clinically are done in quiet rooms, which make it hard to predict how a child, especially one fitted with a hearing aid or cochlear implant, might perform in noisy rooms,” Litovsky says.

Litovsky’s test, on the other hand, simulates the noisy world by including a variety of competing voices and other sounds that children might hear at school, on the playground or at home. Results so far show that some children can separate sounds better than others.

Children who take Litovsky’s test, or “game,” sit in front of a computer surrounded by a semicircle of loudspeakers. They listen for words that match pictures on the screen. Sometimes, they might hear only one voice asking them to point to a particular object. Other times, they might hear several voices coming from either the same location or from different ones. Yet, every time only one voice asks the children to choose an object. To correctly identify it, the children must try to ignore all the simultaneous speakers, except the one giving directions.

“When the voices come from the same place and when we add more competing voices, the task gets more difficult,” says Litovsky, who has tested children as young as 4. But, the researcher has also found that each child’s ability to separate the different speakers varies, most likely due to individual rates of auditory and cognitive development. “Adults are generally much better at this task than children,” she adds, because many aspects of hearing continue to develop into the teenage years.

By varying the test, Litovsky has also found that children have more difficulty separating competing sounds that produce a more audible reverberation, or echo. Binaural hearing generally allows humans to quiet these echoes, but Litovsky says the acoustics of a room can greatly affect this ability.

“The results from these tests lead to interesting questions about the acoustical architecture of classrooms,” she says.

Litovsky will present more of these findings Thursday, June 6, at the annual Acoustical Society of America conference in Pittsburgh.

Litovsky plans to work with children who are born deaf and who receive cochlear implants to restore hearing. Through her work at the Waisman Center, Litovsky plans to use her test to assess how children with developmental disabilities, such as autism, fragile-X and Down syndrome, hear in noisy environments. “To date, almost nothing is known about hearing abilities in children with disabilities,” she says. “In order to be able to help these children function in realistic environments, we must understand how they hear.”

The Wisconsin Alumni Research Foundation has filed a patent on Litovsky’s hearing test. Litovsky hopes that clinicians and researchers will integrate her “game” into the battery of tests used to evaluate children’s hearing.