Comparison of Etymotic insert and TDH supra-aural earphones in auditory brainstem response measurement.

There are few systematic comparisons of Etymotic ER-3A insert earphones versus supra-aural earphones in auditory brainstem response (ABR) measurement. We compared ER-3A insert earphones and two types of supra-aural earphones (TDH-39P and TDH-49P) in a group of normal hearing adults. Acoustic analyses revealed spectral and temporal differences among earphones. Behavioral and ABR thresholds to click stimuli were slightly elevated with the ER-3A compared to the TDH earphones. The ER-3A earphones produced a latency delay, relative to the TDH earphones, that varied from about 0.8 to 1.0 msec, and increased at lower stimulus intensity levels. In addition, ABR wave I amplitude was significantly reduced with the ER-3A earphone. Based on these data, we recommend collection of normative data with the ER-3A earphones prior to their use in ABR measurement.