Comparison of Beyer DT48 and etymotic insert earphones: auditory brain stem response measurements.

Click-evoked auditory brain stem responses (ABRs) were measured using a Beyer DT48 circumaural earphone and an Etymotic ER-3A insert earphone in a group of normal-hearing subjects. Comparisons were made between time waveforms and amplitude spectra for the two transducers. ABR waveforms, latencies, and thresholds were compared for the two transducers. Click-evoked ABR and behavioral thresholds were comparable for the two earphones. In addition, absolute response-component latencies differed by an amount that was equivalent to the travel time introduced by the insert earphone's sound-delivery tube. Inter-peak latency differences were virtually identical. These findings suggest that the insert earphone is a viable transducer for clinical ABR evaluations. Further, a temporal correction may be all that is necessary to account for the difference between the insert earphone and the circumaural earphone if other characteristics of the transducers are similar.