PURPOSE: The purpose of this study was to investigate the prescribed and measured gain of hearing aids fit according to the NAL-NL1 and the DSL v5 procedure for children with moderately severe to profound hearing loss; and to examine the impact of choice of prescription on predicted speech intelligibility and loudness.
RESEARCH DESIGN: Participants were fit with Phonak Naida V SP hearing aids according to the NAL-NL1 and DSL v5 procedures. The Speech Intelligibility Index (SII) and estimated loudness were calculated using published models.
STUDY SAMPLE: The sample consisted of 16 children (30 ears) aged between 7 and 17 yr old.
DATA COLLECTION AND ANALYSIS: The measured hearing aid gains were compared with the prescribed gains at 50 (low), 65 (medium), and 80 dB SPL (high) input levels. The goodness of fit-to-targets was quantified by calculating the average root-mean-square (RMS) error of the measured gain compared with prescriptive gain targets for 0.5, 1, 2, and 4 kHz. The significance of difference between prescriptions for hearing aid gains, SII, and loudness was examined by performing analyses of variance. Correlation analyses were used to examine the relationship between measures.
RESULTS: The DSL v5 prescribed significantly higher overall gain than the NAL-NL1 procedure for the same audiograms. For low and medium input levels, the hearing aids of all children fit with NAL-NL1 were within 5 dB RMS of prescribed targets, but 33% (10 ears) deviated from the DSL v5 targets by more than 5 dB RMS on average. For high input level, the hearing aid fittings of 60% and 43% of ears deviated by more than 5 dB RMS from targets of NAL-NL1 and DSL v5, respectively. Greater deviations from targets were associated with more severe hearing loss. On average, the SII was higher for DSL v5 than for NAL-NL1 at low input level. No significant difference in SII was found between prescriptions at medium or high input level, despite greater loudness for DSL v5 than for NAL-NL1.
CONCLUSIONS: Although targets between 0.25 and 2 kHz were well matched for both prescriptions in commercial hearing aids, gain targets at 4 kHz were matched for NAL-NL1 only. Although the two prescriptions differ markedly in estimated loudness, they resulted in comparable predicted speech intelligibility for medium and high input levels.
METHODS: Four questions and their corresponding response options were adapted from existing population-based surveys to assess tinnitus prevalence, tinnitus symptom severity, use of healthcare resources for tinnitus and hearing difficulty. The translated versions (Bulgarian, French, German, Greek, Italian, Latvian, Polish, Portuguese, Romanian, Russian, and Spanish) were generated using recognized methods to achieve a "world-for-world" translation.
RESULTS: Translated versions were produced with acceptable functional equivalence to the original English-language version, as judged by a small panel of bilingual speakers who participated in the online field testing.
CONCLUSION: This work is the first of its kind to promote multi-national standardization by creating a set of tools that can readily be used across countries. These are currently being used in a European-wide study of tinnitus prevalence, and have wider application across English- and Spanish speaking countries including the Americas and Oceania.