Development of an infant-friendly flat-panel earphone for non-invasive functional brain imaging on awake babies using cartilage conduction

An infant-friendly earphone using the cartilage conduction for non-invasive functional brain imaging was developed. The earphone was composed of a piezoelectric vibrator that is firmly glued to a flat round brass panel, with a diameter of 35 mm, to amplify the vibration. The earphone can be attached to the baby head cap, and just mildly touched to baby's pinna. Since sounds are conveyed via both airand bone-conduction (mainly osseotympanic emission) pathways by the earphone, the enhancement of low frequency component is expected by the occlusion of the ear canal. Clear auditory evoked MEG responses were obtained from awake babies (6-month-old and 8-month-old) as well as adults, using our first prototype flat-panel earphone. Also, the babies did not dislike to wear the developed earphone at all. The earphone enables an experiment of dichotic listening that was quite difficult for awake babies.