Previous studies have shown that adult listeners are more adept than child listeners at identifying spectrally degraded speech. However, the development of the ability to combine speech information from different frequency regions has received little previous attention. The purpose of this study was to determine the effect of age on the bandwidth necessary to achieve a relatively low-criterion level of speech recognition for two frequency bands and then to determine the improvement in speech recognition that resulted when both speech bands were present simultaneously.
Listeners in this study included normal-hearing children (aged 6 to 14 yrs, N = 18) and adults (N = 11). In the first stage of testing, sentences were band pass filtered around either 500 or 2500 Hz, and the bandwidth of that filter was varied adaptively to determine the width required for approximately 15 to 25% correct speech recognition. In the second stage of testing, these criterion bandwidths were presented in fixed block trials with either one band or both bands, and the percent correct performance was determined.
Results suggest that age is inversely associated with the bandwidth required to achieve a relatively low-criterion level of speech recognition for speech bands centered at either 500 or 2500 Hz. However, both adults and children show a similar, large improvement in performance when both bands are presented simultaneously.
Although younger children require more bandwidth to recognize speech filtered around a single frequency correctly, they seem to be relatively adept at integrating frequency-distributed information to recognize a composite stimulus.