Evaluation of hearing aid performance in school-aged children with moderately severe to profound hearing loss fitted according to the NAL-NL1 and DSL v5 prescriptive procedures

"The National Acoustic Laboratories (NAL) and the Desired Sensation Level (DSL) prescriptive procedures are often cited as the most sustainable, validated procedures and the most common methods used for hearing aid fitting in adults and in children. The overall aim of the present study is to evaluate the relative performance of the two procedures in children. The study focuses on children because they are most likely to rely on hearing aids fitted with techniques based solely on prescriptive approach. Sixteen Malaysian children with moderately severe to profound hearing loss were involved in the study. The children were fitted with the Phonak Naida V SP hearing aids based on the NAL-NL1 and DSL v5 prescriptive procedures. The NAL-NL1 and DSL v5 were the latest versions of the respective prescriptive formulae available at the time when this study was carried out. After hearing aid fitting, an extended period of hearing aid trial was given to each child. The relative performance of the two procedures was assessed using speech tests, paired-comparison judgments of speech intelligibility tests and questionnaires completed by the parents, teachers and the children themselves. The questionnaires used in the study were the Parents' Evaluation of Aural/Oral Performance of Children (PEACH), the Teachers' Evaluation of Aural/Oral Performance of Children (TEACH) and the Self Evaluation of Listening Function (SELF). The questionnaires were adapted into the Malay language. Each child also completed a short diary for them to compare the performance of the two procedures in different listening environments. The results showed a significant difference of performance between the NAL-NL1 and DSL v5 procedures for sentence test in quiet and for the subjective measures using questionnaires completed by the parents, teachers and children. The study concluded that the required hearing aid gain for children with moderately severe to profound hearing loss would seem to approximate the DSL v5 prescription, at least in quiet listening environments. The findings have important clinical implications for country like Malaysia where many children with severe to profound hearing loss still rely on hearing aids as their primary amplification devices". -- Abstract.