Revised estimates of hearing aid test system accuracy

This study describes a refinement and extension of a procedure to estimate hearing aid test system accuracy reported by Townsend. The present results were obtained from 10 repeated measures on one linear and one AGC hearing aid. Test system variability, represented by standard deviations (SDs) for the 10 trials, was found to be less than or equal to the manufacturer's specifications for 7 of 8 ANSI S3.22-1976 measurements. Furthermore, 4 of these measures revealed variability of only .1 dB. The stability of the SDs across trials varied depending on the measurement; some were consistently reliable whereas others fluctuated considerably. Although data based on 3 trials differed substantially from the 10-trial results, those from 5 trials indicated only minimal differences.