Towards improved measurements of bone conduction auditory brainstem responses in infants and adults: mitigation of stimulus artefact.

Objective: To reduce the amplitude of stimulus artefacts present in bone conduction auditory brainstem response (BC ABR) measurements.

Design: Electromagnetic shielding was applied to the surface of a clinical BC transducer. A foam pad was also placed on the shielded mastoid-contacting plate of the transducer. Acoustic impacts of these modifications were evaluated using an artificial mastoid. Unmodified and modified (shielding with pad) transducers were then used to elicit BC ABRs in adults and infants. Stimulus artefact amplitudes were compared across transducers.

Study sample: Six adults (24-42 years old) and 13 typically developing infants (mean age 48.77 days) with no sensorineural hearing loss.

Results: Shielding alone slightly decreased acoustic transducer output above approximately 1000 Hz. The addition of a foam pad largely negated this loss, while lower-frequency (500-1000 Hz) acoustic transducer output was slightly increased. The modified transducer produced significantly less stimulus artefact, although variation across subjects was also evident. In a clinical setting, Wave V was detected at similar rates for both transducers.

Conclusion: While artefact was not eliminated, direct attenuation of artefact amplitude (versus software-based mitigation strategies) could simplify BC ABR and other evoked potential measurement protocols and support more stringent artefact rejection criteria to yield more informative recordings.