Air and bone conduction brain stem responses in adults and infants

Air and bone conduction brain stem responses were recorded in 20 adults and 20 infants (16-20 months postconceptional age) with normal hearing. The stimuli were administered using a shielded TDH-39 headphone and a standard B-70A vibrator. Our results show that adults and infants have similar air and bone conduction brain stem thresholds. The comparison of input latency functions obtained with air and bone conduction clicks indicates that the acoustic stimulus generated by the bone vibrator excites more apical regions than that stimulated by the air conduction transient. This is related to the spectrum of the bone conduction click which has an energy peak at 1-2 kHz. Furthermore we found that the difference in latency between adults and infants for air-conducted clicks decreases along with the stimulus intensity and the latencies tend to overlap near the threshold.