Parallel adaptive line enhancers and cartilage conduction to improve speech intelligibility

Cartilage conduction is a sound transmission mechanism that vibrates an aural cartilage to generate sound in the external auditory canal for transmission to the eardrum. The cartilage conduction earphones do not block the ear, allowing users to hear environmental sounds including both desired (e.g., speech) and undesired sounds (e.g., noise) simultaneously. While Active Noise Control (ANC) has been studied to adapt and reduce only the noise, the effect is limited especially when slight white noise masks the speech (i.e., high signal-to-noise ratio (SNR) conditions). In the open-ear hearing aid, the mixed signal is captured by a microphone, but amplifying the signal does not improve the SNR. Therefore, our study focused on speech enhancement using the Adaptive Line Enhancer (ALE). The ALE is an adaptive filter that extracts cyclic signals from uncorrelated noise. Consequently, it can selectively enhance the desired speech and improve the SNR. We also introduce parallel joint of the multiple ALEs to boost this effect. The parallel ALEs demonstrated that higher amplification improved SNR by approximately 10 dB and enhanced the speech intelligibility. When our system is applied to cartilage conduction hearing aids, it will enable users to hear essential daily sounds more clearly in moderate noisy environments.