A comparison of the variability in thresholds measured with insert and conventional supra-aural earphones

The purpose of this study was to evaluate the reliability and comparability of the commercially available insert earphone Etymotic Research ER-3A and the commonly available supra-aural TDH earphone. Thirteen subjects were tested five times with the ER-3A and five times with TDH-49P with MX-41/AR cushions. Threshold determinations were obtained utilizing a sweep-frequency audiometer in the range 0.25-8 kHz. The results showed that the reliability of the ER-3A earphone as measured by intra-individual variation, was comparable to that obtained with the TDH earphone. No evidence was found indicating an increased variability due to the positioning of the insert earphone's coupling device in the ear canal. Comparison of thresholds obtained with both devices indicated that the manufacturer's suggested correction values were appropriate.