Response latencies and amplitudes of cABR evoked using consonant vowel /da/ and compound click-sawtooths sounds
A total of twenty ears from ten healthy participants (5 females and 5 males), aged 69 between 20 and 35 years (average 28 years), were enrolled. All participants had normal hearing acuity that was defined as the pure-tone hearing threshold levels of 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, and 8000 Hz were better than 25 dB HL. The auditory evoked potentials (AEPs) were evoked and acquired by the commercial system (SmartEP, Intelligent Hearing Systems, Miami, USA). The acoustic stimulations were the 40-ms synthetic syllable /da/ (CV-da) and the compound click-sawtooths (CSW) and were delivered by insert earphones (ER-2A) . CSW is an electrically generated sound that starts with a 100-us click, followed by a 10-ms interval of zero amplitude, and finally goes with three cycles of 100-Hz sawtooth. CSW has the same duration of 40 ms as CV-da and similar time-lock features with CV-da, however, is sparse of stimulation energy between click and onset of sawtooth waves as well as between the three sawtooth waves. Electrode montage was non-inverting electrode fixed on high forehead (Fz) and inverting electrodes fixed on both earlobes (Ai). Low forehead (Fpz) served as the reference electrode. AEPs were acquired by averaging two blocks of 2000 repetitions for both stimuli. Peaks V, A, C, D, E, and F of response waveforms were determined, the latency and amplitude of each peak were recorded for statistical analysis. The response amplitudes were significantly greater for CSW and the latencies were significantly shorter for CSW. The latency-intensity functions were also greater for CSW. For CSW, adjustments of energy component can be made without causing biased changes of the other. CSW may also be used in future basic research and clinical applications of cABR.