Non-Linear Frequency Compression and Speech Identification in Children
Hillock-Dunn et al evaluated 17 children (ages 9 to 17 years) with mild-to-profound sensorineural hearing loss (SNHL) with respect to two measures: (1) consonant identification in quiet and (2) spondee identification in noise. The researchers provided the Phonak Naida V SP “laboratory” non-linear frequency compression (NLFC) hearing aid, which allows NLFC to be turned on and off in the same device. Hearing aids were programmed to DSL v 5.0 targets. All participants were full-time users of NLFC and of note, their own ear molds were used across all devices. Baseline measures were acquired using the child’s personal NLFC hearing aids. Therefore, each child was tested for speech perception in three conditions: (1) condition one was their own personal hearing aids with NLFC on, (2) condition two was the laboratory hearing aid with NLFC on, and (3) condition three was the laboratory hearing aid with NLFC off.
The authors report that consonant identification in quiet did not demonstrate a statistically significant difference across the three conditions. They stated that “no systematic differences in the data sets were evident between NLFC on and NLFC off for either the high-frequency or mid-frequency tokens. Average performance was similar with NLFC activated and deactivated for the high-frequency and mid-frequency subsets….” With regard to spondee identification in noise, similar results were found. That is, “no significant effect of NLFC was observed in group data using laboratory hearing aids with NLFC on versus NLFC off…” in speech noise or with a background of two-talker babble.
Hillock-Dunn et al concluded that, “although use of NLFC processing has become increasingly prevalent in pediatric hearing aid fittings, only limited outcome data are available describing its effect on the speech recognition abilities of children….” And they report that “in contrast to previous work, findings from the present study show no consistent benefit or detriment of NLFC….”
For More Information, References, and Recommendations
Hillcock-Dunn A, Buss E, Duncan N, Roush PA, Leibold LJ. (2014) Effects of Non-Linear Frequency Compression on Speech Identification in Children with Hearing Loss. Ear & Hearing 35(3):353-365.