Prescribed real-ear and achieved real-life differences in children's hearing AIDS adjusted according to the NAL-NL1 and the DSL v.4.1 prescriptions

This paper examined how hearing aids adjusted for comparing NAL-NL1 with DSLv.4.1 prescription formulas matched prescriptive targets. The real-ear-to-coupler differences (RECD) of 48 children (24 in Australia and 24 in Canada) were measured and used to derive coupler gain targets. Verification of gain and output were carried out in an HA2-2cc coupler. Electroacoustic measurements revealed a minimal difference between NAL-NL1 and DSLv.4.1 frequency-response slopes due to practical limitations of the devices, even though the prescribed differences were large (up to 13 dB/octave). The difference in overall gain was generally achieved in the hearing aids, with DSLv.4.1 prescribing higher overall gain than NAL-NL1. The mean RECD at 4 kHz was 5 dB higher for children in Australia than in Canada. As the same RECDs were used in deriving targets for both prescriptions, this is unlikely to affect the results of the comparison. The impact of a gain difference between prescriptions on children's performance and preferences in real life is reported in separate papers.