Hearing sensitivity in newborns estimated from ABRs to bone-conducted sounds

This study focused on the problem of estimating hearing sensitivity in newborns from auditory brainstem responses (ABRs) evoked by clicks and 500 Hz and 4000 Hz tonebursts presented by a bone-conduction (BC) oscillator. The effects of acoustic energy transmitted to the ear canal, gender, and ear differences were also investigated. ABR thresholds for BC stimuli were 56, 52, and 53 dB (re 1 microN) or -5, -14, and 0 dB nHL (re adult psychophysical threshold) for click and 500 Hz and 4000 Hz tonebursts, respectively. For newborns, ear canal SPLs generated by the BC stimuli were as much as 21 dB greater than those in adults. Gender-related threshold differences were significant, with female infants having lower thresholds than males; however, ear differences were not. The findings of this study can be used to set appropriate BC stimulus levels for screening or assessment of newborns.