Improvement method for sound quality of pharyngeal speech by using Bayes' theorem

In general, a speech signal can be measured by a microphone and a pharyngeal microphone etc.. However, speech signal measured by a microphone often contains the background noise. On the other hand, though a pharyngeal microphone is effective for background noise, it involves body conducted noise. In this study, we propose an improvement method for sound quality of speech signal measured trough a pharyngeal microphone to achieve well the speech recognition. The relationship between the original speech signal and the speech measured by the pharyngeal microphone is not clear. Therefore, we consider the relationship as multiplicative and additive models of the original speech signal and noise components with unknown parameters. An algorithm to estimate simultaneously the original speech signal and the unknown parameters is proposed by using Bayes' theorem based on the measured speech through the pharyngeal microphone. Finally, a speech recognition experiment is conducted to confirm the effectiveness of the proposed algorithm.