Perceptual Implications of Level- and Frequency-Specific Deviations from Hearing Aid Prescription in Children

The purpose of providing amplification for children with hearing loss is to make speech audible across a range of frequencies and intensities. Children with hearing aids (HAs) that closely approximate prescriptive targets have better audibility than peers with HA output below prescriptive targets. Poor aided audibility puts children with hearing loss at risk for delays in communication, social, and academic development.

The goals of this study were to determine how well HAs match prescriptive targets across ranges of frequency and intensity of speech and to determine how level- and frequency-dependent deviations from prescriptive target affect speech recognition in quiet and in background noise.

One-hundred sixty-six children with permanent mild to severe hearing loss who were between 6 months and 8 years of age and who wore HAs participated in the study.

Hearing aid verification and speech recognition data were collected as part of a longitudinal study of communication development in children with HAs. Hearing aid output at levels of soft and average speech and maximum power output were compared with each child's prescriptive targets. The deviations from prescriptive target were quantified based on the root-mean-square (RMS) error and absolute deviation from target for octave frequencies. Children were classified into groups based on the number of level-dependent deviations from prescriptive target. Frequency-specific deviations from prescriptive target and sensation levels (SLs) were used to estimate the proximity of fittings across the frequency range. Lexical Neighborhood Test (LNT) word recognition in quiet and Computer-Assisted Speech Perception Assessment (CASPA) phoneme recognition in noise were compared across level-dependent error groups and as a function of SL at 4 kHz.

Children who had deviations from prescriptive target at all three input levels had poorer LNT word recognition in quiet than children who had fittings that matched prescriptive target within 5 dB RMS at all three input levels. Children with lower 4 kHz SLs through their HAs had poorer LNT recognition in quiet and CASPA phoneme recognition in noise than children with higher aided SLs.

Children with HAs fitted to provide audibility for speech across a range of inputs and frequencies had better speech recognition outcomes than peers with HAs that were not optimally fitted to prescriptive targets.