Development of low-frequency tone burst versus the click auditory brainstem response.

Often ABR threshold testing employs clicks to assess high-frequency hearing, and low-frequency tone bursts to assess low-frequency sensitivity. While a maturation effect has been shown for click stimuli, similar data are lacking for low-frequency toneburst stimuli. Thus, 305 infants ranging in conceptional age (CA) from 33 weeks to 74 weeks were tested. Absolute latencies were measured for wave V at 55, 35, and 25 dB nHL in response to a click and for wave V500 in response to a 500 Hz tone burst. Major wave latency in response to 500 Hz tone bursts decreases with age and do not stabilize by 70 weeks CA. Likewise, waves III and V latencies in response to clicks decrease with age, as has been reported by others, and do not stabilize by 70 weeks CA. Wave I latency produced by clicks did not decrease with age, being mature by 33 weeks CA.