Digital inverse filtering of distorted auditory brainstem responses.

Analogue filtering of source data can cause severe distortion of ABR waveform, primarily due to filter phase non-linearity. This distortion contributes to incompatibility between laboratories. Digital zero-phase filtering of the average ABR obtained with wide bandwidth gives much less distortion, but can cause difficulties with data acquisition protocols. We have investigated digital phase-correction of distorted average ABRs recorded with conventional filters. The method is successful and feasible. It is also possible to digitally recover the ABRs that would have been obtained with wider recording bandwidths, or with different filter orders. This approach can be used for conversion of ABR waveforms to a standard low-distortion filter condition, or to convert between conventional filter conditions used in different laboratories.