Notched-Noise Measures of Frequency Selectivity in Adults and Children Using Fixed-Masker-Level and Fixed-Signal-Level Presentation Three experiments were performed to examine the development of frequency selectivity and to attempt to separate peripheral versus central contributions to frequency selectivity. In Experiment 1, frequency selectivity was examined in 4-year-old children, 6-year-old children, and adults, using a fixed-masker-level, notched-noise masking method. Thresholds were determined in a no-notch condition ... Research Article
Research Article  |   June 01, 1991
Notched-Noise Measures of Frequency Selectivity in Adults and Children Using Fixed-Masker-Level and Fixed-Signal-Level Presentation
 
Author Affiliations & Notes
  • Joseph W. Hall, III
    Division of Otolaryngology/Head & Neck Surgery, University of North Carolina Medical School Chapel Hill
  • John H. Grose
    Division of Otolaryngology/Head & Neck Surgery, University of North Carolina Medical School Chapel Hill
  • Requests for reprints should be sent to Joseph W. Hall III, PhD, Division of Otolaryngology/Head and Neck Surgery, University of North Carolina Medical School, CB#7070, Burnett-Womack Clinical Sciences Building, Chapel Hill, NC 27599-7070.
Article Information
Hearing / Research Articles
Research Article   |   June 01, 1991
Notched-Noise Measures of Frequency Selectivity in Adults and Children Using Fixed-Masker-Level and Fixed-Signal-Level Presentation
Journal of Speech, Language, and Hearing Research, June 1991, Vol. 34, 651-660. doi:10.1044/jshr.3403.651
History: Received January 8, 1990 , Accepted August 30, 1990
 
Journal of Speech, Language, and Hearing Research, June 1991, Vol. 34, 651-660. doi:10.1044/jshr.3403.651
History: Received January 8, 1990; Accepted August 30, 1990

Three experiments were performed to examine the development of frequency selectivity and to attempt to separate peripheral versus central contributions to frequency selectivity. In Experiment 1, frequency selectivity was examined in 4-year-old children, 6-year-old children, and adults, using a fixed-masker-level, notched-noise masking method. Thresholds were determined in a no-notch condition and in conditions in which the notchwidth was 0.3 times the center frequency (0.3 x fc) or 0.6 x fc. The results for the adults and 6-year-olds were similar, but the notched-noise functions of the 4-year-old listeners were relatively shallow. These results were consistent with an interpretation that frequency selectivity is relatively poor in 4-year-old listeners; however, the results of the 4-year-old listeners might also be accounted for in terms of poor processing efficiency. For example, the children may require a relatively high level of signal-related excitation in order for detection to occur. If the growth of excitation is steeper in the no-notch condition than in notched-noise conditions, then thresholds in the notched-noise conditions might be elevated because of poor processing efficiency rather than poor frequency selectivity. This interpretation is consonant with past data showing that the growth of loudness of partially masked signals steepens as a function of increasing masker level: The masker level at the output of the auditory filter centered on the signal frequency would be less for the notched-noise masker than for the masker having no notch. In Experiment 2 the growth of loudness was examined for three adult listeners in the no-notch condition and the 0.6 x fc notched noise. Results showed a steeper growth of loudness in the no-notch case. In Experiment 3, a notched-noise measure of frequency selectivity was used in which the signal level was fixed at 15 dB SL and the masker level was varied adaptively. In this method the noise level at the output of the auditory filter centered on the signal should theoretically be constant over the different notch conditions. Adult and 4-year-old listeners were tested. The notched-noise functions were similar between the adult and 4-year-old listeners. This result supports an interpretation that the shallow notched-noise, fixed-masker-level functions of 4-year-old children may be due to poor processing efficiency rather than to poor peripheral frequency selectivity.

Acknowledgments
This work was supported by a grant from NIH R01-DC00397. We thank two anonymous reviewers for their helpful comments. We also thank Deborah Hatch and Pat Geer for their help in the collection of data.
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