抄録
Effects of analog filtering on the auditory middle latency responses (MLR) in young children synthesized by a complex waveform synthesizer were studied. For obtaining analog-filtered responses, a Butterworth filter was used with a passband from 20 or 25Hz to 175Hz and a roll-off slope of 24dB/octave.
Analysis of the analog-filtered responses revealed that the first negative peak (Na) and the second positive peak (Pa) in the filtered response were resulted from the filter-produced damped oscillations of the preceeding peaks of ABR (Po) and Na in the unfiltered responses, respectively. Likewise, the second negative peak (Nb) and the third positive peak (Pb) in the filtered responses were composed of the filter-generated oscillations triggered by Na and the later components of the unfiltered responses. The results showed that the MLR waveforms in young children were radically distorted by analog high-pass filtering at 20-25Hz with a roll-off slope of 24dB/octave. It can be meaningless to compare directly these filtered responses with the unfiltered ones.
