Bone Conduction Chirp Auditory Brainstem Response: Transducer-Specific Optimization and Validation in Normal-Hearing Adults

Objective: Chirp stimuli are widely adopted for air-conduction auditory brainstem response (ABR) testing, yet bone-conduction (BC) chirp ABR remains relatively understudied. This study evaluated whether a transducer-specific BC chirp stimulus and individualized sensation-level calibration improve BC ABR performance compared with conventional BC click stimulation.

Methods: Twenty-four normal-hearing adults (30 ears; 19–30 years) underwent ABR testing using BC chirp (0.1–4 kHz), BC click, AC band-limited chirp (0.1–4 kHz), AC broadband chirp (0.1–10.4 kHz), and AC click stimuli. Psychoacoustic thresholds were measured for each stimulus and ear and used as individual reference levels (dB SL). Outcome measures included threshold accuracy, Wave V amplitude, latency–intensity characteristics, and waveform replicability.

Results: BC chirp produced significantly more accurate threshold estimates than BC click, reducing the mean ABR-to-psychoacoustic threshold difference from 13.83 dB SL to 6.50 dB SL (p < 0.001). Wave V amplitudes were significantly larger for BC chirp at 20 and 40 dB SL (p < 0.001), and latency–intensity slopes were steeper than those obtained with BC click (p < 0.001). No differences were observed in waveform replicability. Band-limited and broadband AC chirp stimuli demonstrated equivalent performance.

Conclusions: A transducer-specific BC chirp significantly improves threshold accuracy and response amplitude compared with conventional BC click stimulation. These findings support the use of individualized calibration and transducer-matched stimulus design for improving objective threshold estimation in bone-conduction ABR assessment.