A cross-over, double-blind comparison of the NAL-NL1 and the DSL v4.1 prescriptions for children with mild to moderately severe hearing loss

The relative effectiveness of the NAL-NL1 and the DSL4.1 prescriptions for 48 children with mild to moderately severe hearing loss was studied using a double-blind, four-period, two-treatment cross-over design in Australia and in Canada. Evaluations included speech perception tests, loudness ratings, reports from parents and teachers on functional performance in real life, children's self-reports, paired-comparison judgements of intelligibility, and children's preferences in real-world environments. Electroacoustic measures of hearing aids revealed that gain differences dominated the comparison. Across trials and measures, individual Australian children consistently preferred either the NAL-NL1 or the DSL v.4.1 prescription. An overall figure of merit (FOM), calculated by averaging the standardized difference scores between prescriptions for all measures, revealed that the strongest prescription-related differences were found in Australia. On average, an advantage and preference for the NAL-NL1 prescription was associated with lesser degrees of hearing loss. This research provides evidence on the effectiveness of the NAL-NL1 and DSL v.4.1 prescriptions, and highlights the need for evaluating and fine-tuning amplification to meet the diverse needs of individual children in real life.