Analogue and digital filtering of auditory brainstem responses

Area of Science:

• Neuroscience
• Audiology
• Signal Processing

Background:

• Auditory brainstem responses (ABRs) are crucial for assessing auditory pathway function.
• Digital signal processing offers advanced analysis capabilities for ABRs.
• Traditional filtering methods can introduce artifacts and alter ABR characteristics.

Purpose of the Study:

• To investigate the impact of high-pass filtering on ABR waveforms.
• To evaluate the effectiveness of zero phase filtering in reducing ABR distortion.
• To assess the feasibility of off-line digital filtering for ABR data.

Main Methods:

• Recorded wide-bandwidth ABRs from normal adults using 70 dB nHL clicks.
• Applied variable band-pass and high-pass filters (20-500 Hz) digitally.
• Compared results from different filter orders and types (Butterworth, boxcar).
• Utilized zero phase filtering for distortion analysis.

Main Results:

• High-pass filtering (20-500 Hz) caused significant ABR waveform distortion, including artifactual peaks and altered latencies.
• Distortion increased with filter order.
• Zero phase filtering substantially reduced ABR distortion and latency changes.
• Filter phase distortion was a major contributor to mean square error at common high-pass frequencies.

Conclusions:

• Off-line digital filtering of ABRs is technically feasible and beneficial.
• Zero phase filtering is recommended to minimize distortion and preserve ABR waveform integrity.
• Digital filtering facilitates inter-laboratory data comparison and standardization.