A comparison of two non-linear prescriptive methods used with digital hearing instrument fittings in children

Abstract

Advances in hearing instrument technology have permitted the development of non-linear prescriptive methods to prescribe amplification characteristics for the hearing- impaired individual. The dispenser’s task in selecting the most appropriate prescriptive procedure for the young child is of utmost importance to ensure optimum hearing aid benefit for communication development. It was the aim of this study to compare and describe the effect of the two most widely used methods, DSL (i/o) and NAL-NL1, on speech recognition and loudness perception. An exploratory, descriptive research design was selected to realise this goal. Ten participants were selected using a convenient non-probability method of sampling. Articulation index calculations and a closed set speech recognition test were utilised in the evaluation of speech recognition, whereas functional gain results and loudness rating measurements provided an opportunity to describe loudness perception. The obtained results were analysed using the SAS (Statistical Analysis System). The study concluded that, although significant statistical differences existed in loudness perception, no statistical difference was observed in actual speech recognition measures. This effect may contribute to the individual amplification approaches of the two methods, which seem to reflect the uncertainties expressed by researchers as to the contribution of high frequency amplification to speech recognition in young children.