Auditory Steady-state Responses to Chirp Stimuli Based on Cochlear Traveling Wave Delay

This study investigates the use of chirp stimuli to compensate for the cochlear traveling wave delay. The temporal dispersion in the cochlea is given by the traveling time, which in this study is estimated from latency-frequency functions obtained from (1) a cochlear model, (2) tone-burst auditory brain stem response (ABR) latencies, (3) and narrow-band ABR latencies. These latency-frequency functions are assumed to reflect the group delay of a linear system that modifies the phase spectrum of the applied stimulus. On the basis of this assumption, three chirps are constructed and evaluated in 49 normal-hearing subjects. The auditory steady-state responses to these chirps and to a click stimulus are compared at two levels of stimulation (30 and 50 dB nHL) and a rate of 90s. The chirps give shorter detection time and higher signal-to-noise ratio than the click. The shorter detection time obtained by the chirps is equivalent to an increase in stimulus level of 20 dB or more. The results indicate that a chirp is a more efficient stimulus than a click for the recording of early auditory evoked responses in normal-hearing adults using transient sounds at a high rate of stimulation.