Bone Conduction Threshold Estimation with Sofi® using Rapid-CAEP®

Bone Conduction Threshold Estimation with Sofi® using Rapid-CAEP®

Authors: Rohit Vijayakumar¹, Timothé Guyonnet Hencke¹, Oscar Portoles¹, Mark van Kesteren¹

¹MindAffect B.V.

Background: The current ‘gold standard’ of (BC) audiometry relies on subjective behavioral responses, which are challenging for populations including young children and individuals with disabilities. Sofi is a novel audiometric assessment system using Rapid Cortical Auditory Evoked Potentials (Rapid-CAEP) with 8 water-based EEG electrodes and a 12.5-minute testing time to objectively estimate BC thresholds with 5 dB HL resolution for multiple tone frequencies.

Methods: 30 datasets were collected from participants with asymmetrical sensorineural hearing loss. BC thresholds were assessed at 500, 1000, 2000, and 4000 Hz using a bone transducer placed on the mastoid of the poorer-hearing ear. Thresholds were estimated with three methods: Sofi, pure tone audiometry (PTA), and a modified Hughson-Westlake behavioral procedure (autoBEH) using the same auditory stimulation as Sofi. The autoBEH served as a calibration reference to account for systematic differences between Sofi and PTA. Threshold estimates from Sofi, PTA, and autoBEH were compared using Spearman’s correlation (ρ), orthogonal distance regression, and mean absolute difference (MAD).

Results: Threshold comparisons between Sofi and autoBEH showed intercepts close to 0 across frequencies (intercept < ± 5 dB HL, R² > 0.79, p < 0.001). In contrast, larger intercepts were observed between PTA and autoBEH (intercept up to ± 10 dB HL), suggesting systematic differences between the stimulation modalities. A strong statistically significant monotonic relationship was observed between Sofi and PTA thresholds (ρ = 0.65, p < 0.001), with the correction of systematic differences reducing the mean absolute difference to 9.33 dB HL across tone frequencies.

Conclusions: The strong Spearman’s correlations and MADs within 10 dB HL between Sofi and PTA thresholds support the validity of using Sofi with Rapid-CAEP to objectively estimate bone conduction (BC) hearing thresholds. Future work will aim to extend Sofi to include BC masking conditions.