Abstract:
Introduction: Chirp stimuli are designed to compensate for the temporal delays of the basilar membrane and result in increased neural synchrony. This study aims to compare the performance of chirp and toneburst stimuli in air and bone conduction auditory brainstem response (ABR), characterise the stimulus artefact from stimuli delivered via bone conduction and assess if this affects the efficiency of chirp. Methods: 26 participants were tested with either 2 or 0.5 kHz narrowband (NB) level-specific (LS) CE-Chirp® and toneburst stimuli. Only one ear was tested for each participant. Air conduction testing was carried out at 20, 30 and 40 dB nHL and bone conduction testing was carried out at 20, 30 and 50 dB nHL. The stopping criteria used was 40 nV residual noise. The wave V amplitude, signal-to-noise ratio (SNR), number of sweeps accepted and F for multiple points statistic (Fmp, a statistical analysis of response presence) were measured for each waveform. Results: The wave V amplitude and SNR of the air conduction stimuli were significantly larger for 2 kHz chirp stimuli, but not for 0.5 kHz. There was a significant difference in the Fmp value at 2 kHz and 0.5 kHz. The wave V amplitude, SNR and Fmp were significantly larger for chirp stimuli compared to toneburst delivered via bone conduction, with the exception of Fmp at 0.5 kHz. There was no significant difference in the number of sweeps accepted for the two stimulus types for both air and bone conduction ABR, except for at 0.5 kHz bone conduction. The bone conduction stimulus artefact was also significantly larger than for chirp for both at both frequencies, but this did not result in a difference in the number of sweeps accepted or rejected. Conclusion: ABRs evoked by chirp stimuli show increases in amplitude and SNR compared to toneburst for both air and bone conduction ABR. Although the chirp stimulus delivered via bone conduction produced larger stimulus artefacts, this did not significantly affect the efficiency of the chirp stimuli. These results provide evidence that bone-conducted NB LS CE-Chirp® provide the same advantage as air-conducted chirp.
