Normative wave V latency-intensity functions using the EARTONE 3A insert earphone and the Radioear B-71 bone vibrator

Early auditory evoked response (ABR) audiometry is useful for estimating auditory sensitivity in infants and other difficult-to-test populations. Several investigators advocate using bone-conducted stimuli, in addition to air-conducted stimuli, for screening infants with hearing loss or for ascertaining the presence and magnitude of a conductive hearing loss. The present study was designed to gather normative Wave V latency-intensity data with an insert earphone (EARTONE 3A) and a bone vibrator (Radioear B-71). Forty normal-hearing subjects were tested with air-conducted and bone-conducted clicks at intensities of 55, 40, 30, 20, and 10 dB SL. The stimulus waveforms showed a click onset delay of 0.1 ms for the bone vibrator and 1.0 ms for the 3A insert earphone. It is important to note that our ABR latencies were not adjusted to account for these differences. The results revealed that both the air-conduction and bone-conduction functions exhibited Wave V latencies of 7.0 ms at 55 dB SL. Although both functions exhibited increased latencies as intensity decreased to 10dB SL, the air-conducted clicks yielded somewhat longer latencies than the hone-conducted clicks. To allow direct comparison of the air-conduction and bone-conduction latency-intensity functions, the bone-conduction function must be corrected by approximately +0.3 ms at 40 dB, +0.4 ms at 30 dB, +0.5 ms at 20 dB, and +0.8 ms 10 dB nHL. No correction is needed at 55 dB. The present study suggests that it may not be appropriate to apply a single correction value (e.g., 0.5 ms) to the entire latency-intensity function. If clinicians elect to use published latency-intensity data, they must employ procedures similar to those that were used to collect the normative data. Otherwise, individual clinics should generate normative latency-intensity data using well-delined procedures. An alternative to generating latency-intensity functions is to compare ABR air-conduction and bone-conduction thresholds. This procedure is advantageous because threshold responses are not as sensitive as latency measures to slight changes in instrumentation and procedures. The normative air-conduction and/or bone-conduction values presented in this investigation are offered as a baseline for either latency-intensity or threshold comparisons.