Comparison of Auditory Brainstem Responses Elicited by 4000 Hz Tone-Pips with Gaussian Envelope and Different Width of Acoustic Spectra in Subjects with High-Frequency Hearing Loss

摘要

At present, an objective examination of hearing threshold is performed primarily by means of click-evoked auditory brainstem responses (ABR). Optionally, one evaluates the 500 Hz threshold using a tone pip. However, it is frequently postulated that the hearing threshold should be evaluated more precisely at different frequencies in the speech frequency band - 1000, 2000 and 4000 Hz, especially in the case of young children and subjects with noise-induced hearing loss. The parameters of tone pips with nonlinear envelopes, applicable in ABR threshold examination, have not been standardized yet. The aim of the study was to determine an optimum rise-lime of a 4000 Hz tone pip with Gaussian envelope. The authors examined the influence of spectral bandwidth of the 4000 Hz tone pip on the thresholds of auditory evoked brainstem responses in subjects with high-frequency hearing loss. The bandwidth of the acoustic spectrum of the stimulus was controlled by applying different rise-times of the tone pip, equal to 2, 4, 8 and 16 cycles. The comparison of wave V and auditory thresholds for 4000 Hz obtained for individual stimuli showed that the optimum rise-time of the 4000 Hz pip was equal to 8 cycles. The results of this study showed that acoustic spectrum of tone pips has a significant effect on the differences between audiometric and ABR thresholds in ears with a steeply sloping high-frequency hearing loss.