Efficacy of NAL-NL1 Prescription for the First-Time Hearing Aid Users: A Follow-Up Study

Abstract

A prescriptive approach to hearing aid fitting is one in which the amplification characteristics are calculated from some of the hearing characteristics of an individual. NAL- NL1, one such generic formula, which aims at maximizing speech intelligibility, is widely in use. The aim of the study was to evaluate the efficacy with which NAL-NL1 prescribes the hearing aid parameters for persons with varying types and degrees of hearing loss. In addition to find out the changes in the amplification parameters preferred by the hearing aid users in terms of, after the first 6 to 8 weeks of hearing aid use. Further, the study also aimed at evaluating the extent of deviation of the amplification parameters from the target prescribed by NAL-NL1. For this, a follow-up study was undertaken, in which participants (N=20) were tested under three conditions of hearing aid program. The three hearing aid programs were one with NAL-NL1, second with preferred setting and third with fine tune setting. Both subjective (aided thresholds, Speech reception scores and uncomfortable level) and objective (real ear insertion gain and real ear saturation response) measurements were carried out to compare performance of the participants in the three conditions. The results indicated an improved performance in subjective measures with fine tune settings compared to the other two conditions. These findings were supported by the objective test results also. These findings prove that fine tune program provides better results when compared to NAL-NL1. Re-programming according to individual’s listening needs can enhance the benefit that one derives from the hearing aid. Hence, follow-up of the hearing aid users for fine tuning of the hearing aid should be considered as an integral part of hearing aid prescription procedure for greater user satisfaction and continued hearing aid use.