We used ABR as an objective audiometry or an early indicator detecting the disorders of central nervous system. But the effects of sedatives or bandpass filter on it are still controversial. The ABRs of 20 ears were recorded and analyzed before and after sedation, changing the spectrum of bandpass filter. The results were as follows ; 1) The latencies and interpeak latencies showed unremarkable changies on sedation or change of filtering spectrum. Changies on sedation or change of filtering spectrum. 2) The amplitudes increased remarkably not on sedation but on broad bandpass filtering. So, we propose broad bandpass filter rather than narrow band pass filter for the sharp and less distorted waves.