Ruth A. Bentler, Ph.D., is a Professor and the Director of Audiology Studies in the Department of Communication Sciences and Disorders at the University of Iowa.

For hearing-aided children with moderate to severe hearing loss it can be said that the better the children's auditory/linguistic experiences, the better the children's outcomes are likely to be in a number of realms. But gauging the audibility and quality of hearing-impaired children's typical daily language and audio environments remains difficult. To obtain this type of information researchers and clinicians typically rely on feedback from parents or caregivers.

Transcending these limitations with the objective LENA System, my colleagues at the University of Iowa, University of North Carolina, and Boys Town National Research Hospital and I are trying to answer tough questions concerning these children. For example, How much of the ongoing language and audio that they're exposed to is actually audible and useful? What is the “dosage” of the audible language? Is the audio poor or rich in quality? Will a child wearing a well-fit hearing aid only one hour per day achieve a better language-learning opportunity than one wearing a poorly fit hearing aid for 10 hours a day? And so on.

To investigate these questions with LENA, however, we had to account for the difference in the position of the LENA Digital Language Processor (DLP), worn on children's chests, and the location of the hearing aid, worn on children's ears. By applying a transfer function to the sound levels that were picked up by the chest-level microphone of the DLP, we are able to estimate the sound levels (across a range of frequencies) that reach the hearing aid's microphone. We are then able to transform the signal to the level of the microphone of the hearing aid. Using this input across frequencies, along with the children's audiograms and hearing aid amplification characteristics, we are able to better quantify the audibility accessed over the course of a typical day (the DLP has up to 16 hours of capacity). Our goal now is to develop an algorithm that will represent the summed “dosage” of that meaningful input for a given period.

In other words, by utilizing the ability of LENA to access both the type and level of input stimulus, we will not only be able to quantify the richness of the children's language and audio environments but also how much of that sound is actually audible enough to be meaningful to the children.

This work is part of our longitudinal study to assess speech, language, educational, and psychosocial outcomes, “Moderators of Functional Outcomes in Children with Mild to Severe Hearing Loss,” funded by the National Institutes of Health – National Institute on Deafness and Other Communication Disorders (NIH-NIDCD, Grant No. DC009560). In addition to collecting data on how the hearing aid processes and amplifies the sound picked up by the microphone, we can quantify the audibility of the important speech frequencies. In the final stage of the study, we will estimate hearing aid use time to arrive at a summed dosage of meaningful sound.

With the assistance of NIH-NIDCD and LENA, we hope to prove our primary hypothesis: that audibility drives speech and language development and, ultimately, educational and psychosocial success.