Objective
Adult auditory brainstem response (ABR) amplitudes are employed by both researchers and clinicians, but exhibit substantial between-subject variability, reducing their sensitivity as measures of underlying auditory health. One source of variability is sex, for which a number of mechanisms have been proposed. The present analysis aimed to determine whether ear-canal size influences ABR wave I amplitude, independent of sex.

Design
ABR wave I amplitudes and estimates of ear-canal diameter and volume were obtained from 220 otologically healthy teenagers. Multiple linear regression models tested for independent effects of sex and ear-canal size on ABR amplitudes.

Study sample
Participants were enrolled in a longitudinal study conducted by the Manchester Centre of Audiology and Deafness. The present data were gathered at baseline (age 16–17 years).

Results
The size of the sex effect on wave I amplitude was reduced by adding ear-canal diameter or volume to the model, but it remained significant. Ear canal diameter contributed modestly to wave I amplitude, independent of sex. Ear-canal volume produced null results.

Conclusions
Findings are preliminary and strictly exploratory, but suggest that women’s larger ABR amplitudes may be explained in part by their smaller ear canals, with implications for the sensitivity, comfort, and safety of ABR testing.