A comparison of NAL and DSL prescriptive methods for paediatric hearing-aid fitting: Predicted speech intelligibility and loudness
Johnson, Earl E.
Van Buynder, Patricia
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OBJECTIVE—To examine the impact of prescription on predicted speech intelligibility and loudness for children. DESIGN—A between-group comparison of Speech Intelligibility Index (SII) and loudness, based on hearing aids fitted according to NAL-NL1, DSL v4.1, or DSL m[i/o] prescriptions. A withingroup comparison of gains prescribed by DSL m[i/o] and NAL-NL2 for children in terms of SII and loudness. STUDY SAMPLE—Participants were 200 children , who were randomly assigned to first hearing-aid fitting with either NAL-NL1, DSL v4.1, or DSL m[i/o]. Audiometric data and hearing aid data at 3 years of age were used. RESULTS—On average, SII calculated on the basis of hearing-aid gains were higher for DSL than for NAL-NL1 at low input level, equivalent at medium input level, and higher for NAL-NL1 than DSL at high input level. Greater loudness was associated with DSL than with NAL-NL1, across a range of input levels. Comparing NAL-NL2 and DSL m[i/o] target gains revealed higher SII for the latter at low input level. SII was higher for NAL-NL2 than for DSL m[i/o] at mediumand high-input levels despite greater loudness for gains prescribed by DSL m[i/o] than by NALNL2. CONCLUSION—The choice of prescription has minimal effects on speech intelligibility predictions but marked effects on loudness predictions.