Development and evaluation of pk-Ctone: A computationally efficient strategy for enhanced Mandarin tone perception in cochlear implants

Conventional cochlear implant (CI) strategies convey limited tonal information. Although fundamental frequency (F0)-based strategies, such as C-tone, which combines F0 extraction with amplitude envelope modulation, improve Mandarin tone perception, their high computational demands hinder integration into power- and resource-constrained devices. This study evaluates a lexical tone enhancement CI strategy, pk-Ctone, that employs a computationally efficient local extrema-based F0 detection algorithm. Acoustic evaluations on two Mandarin monosyllabic corpora assessed both the coarse-scale robustness and fine-scale fidelity of F0 detection. Computational operations required for F0 extraction were quantified, and a clinical trial with 62 participants compared Mandarin speech recognition using pk-Ctone versus a standard envelope-based baseline. Results showed that pk-Ctone reduced the computational operations for F0 extraction by more than 30-fold compared with C-tone. Although this efficiency gain incurred a penalty in fine-scale precision, pk-Ctone achieved improved coarse-scale robustness, as quantified by Accuracy and F1-score. Clinically, pk-Ctone yielded significant improvements in recognition of monosyllabic tones (+10.1% points, pp), monosyllabic words (+19.2 pp), and disyllabic words (+13.0 pp). These findings indicate that pk-Ctone, by preserving coarse-scale F0 tracking robustness while reducing computational cost, maintains clinical effectiveness despite some loss in fine-scale precision, offering a practical solution for power- and resource-constrained CI processors.