Testing Hearing by Simulating Sounds

A new hearing test has been developed 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.

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. The present 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 this test 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.The task is graded in difficulty level by adding more competing voices. Though the test has been used on children as young as 4 years, the lead researcher, Ruth Litovsky from the University of Wisconsin-Madison 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.

In the future, 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, and in order to be able to help these children function in realistic environments, the mechanism of how we hear must be understood.