Selection of the optimal rise time of tone pips of 1000, 2000 and 4000 Hz to elicit auditory brainstem responses at high intensity in normal hearing subjects

In clinical practice, the auditory brainstem responses are used for objective evaluation of hearing threshold and in the diagnosis of retrocochlear hearing loss. In the latter case, the examination is performed by means of a click stimulus' which allows assessment of neural conduction time in the auditory nerve and in the brainstem in high frequency region. Tone pips make it possible to evaluate the neural transmission at other frequencies, but ABRs should be frequency specific. One of the methods that can improve frequency specificity of auditory brainstem responses elicited by a tone pip consists in narrowing the acoustic spectrum of stimulus. The aim of this study was to determine an effective rise-time of a tone pip with Gaussian envelope at frequencies 1000, 2000 and 4000 Hz used for eliciting auditory brainstem responses at intensity level of 80 dB nHL. The chosen rise-times were 2, 4, 8 and 16 periods of the tone frequency. On the basis of the analysis of amplitude and occurrence of the V wave in the responses, one determined optimal rise time of the stimulus for each frequency. The results of this study have shown that the longest rise-time values are equal to 4 cycles at 1000 Hz frequency, and 8 cycles at frequencies of 2000 and 4000 Hz.