Improvement of electrolaryngeal speech quality using a supraglottal voice source with compensation of vocal tract characteristics.

Electrolarynx (EL) is a medical speech-recovery device designed for patients who have lost their original voice box due to laryngeal cancer. As a substitute for human larynx, the current commercial EL voice source cannot reconstruct natural EL speech under laryngectomy conditions. To eliminate the abnormal acoustic properties of EL speech, a supraglottal voice source with compensation of vocal tract characteristics was proposed and provided through an experimental EL(SGVS-EL) system. The acoustic analyses of simulated EL speech and reconstructed EL speech produced with different voice sources were performed in the normal subject and laryngectomee. The results indicated that the supraglottal voice source was successful in improving the acoustic properties of EL speech by enhancing low- frequency energy, correcting the shifted formants to normal range, and eliminating the visible spectral zeros. Both normal subject and laryngectomee also produced more natural vowels using SGVS-EL than commercial EL, even if the vocal tract parameter was substituted and the supraglottal voice source was biased to a certain degree. Therefore, supraglottal voice source is a feasible and effective approach to improving the acoustic quality of EL speech.