A compact piezoelectric inertial bone-conduction transducer with broadband vibration response

Abstract

Externally worn bone-conduction devices suffer from high-frequency vibration attenuation induced by the low-pass filtering effect of the skin-soft-tissue layer during transcutaneous vibration transmission. Meanwhile, conventional electromagnetic transducers struggle to balance broadband output with compact and lightweight design. To address this issue, a compact piezoelectric inertial bone-conduction transducer with broadband vibration response is proposed in this paper. By employing a cantilever-proof-mass structure to realize an inertial driving mode, the proposed transducer converts direct-displacement coupling into inertial reaction-force excitation, thereby changing the dynamic force-transmission path between the piezoelectric structure and the viscoelastic load. To overcome the limitations of single-parameter characterization, a multidimensional evaluation method combining electromechanical and threshold-weighted spectral metrics is established. Systematic comparative experiments show that, compared with a commercial electromagnetic benchmark under the common prescribed test conditions used in this study, the proposed piezoelectric prototype achieves reductions of 44.4 % in volume and 22.9 % in mass. Its threshold-weighted effective bandwidth ( B W -10 dB ) reaches 3270 Hz, representing a 9.1 % increase, and its average threshold-weighted velocity level ( L avg ) over 1–4 kHz is 6.9 dB higher. Furthermore, frequency–response fluctuations are reduced, resulting in a smoother and more uniform response. These results demonstrate the potential of piezoelectric inertial excitation as a compact structural approach for improving broadband vibration transmission in wearable bone-conduction audio devices under controlled loading conditions.