Electrolaryngeal speech modification towards singing aid system for laryngectomees

Abstract

Towards the development of a singing aid system for laryngectomees, we propose a method for converting electro-laryngeal (EL) speech produced by using an electrolarynx into more naturally sounding singing voices. Singing by using the electrolarynx is less flexible because the pitch of EL speech is determined by the source excitation signal mechanically produced by the electrolarynx, and therefore, it is necessary to embed melodies of songs to be sung in advance to the electrolarynx. In addition, sound quality of singing voices produced by the electrolarynx is severely degraded by an adverse effect of its mechanical excitation sounds emitted outside as noise. To address these problems, the proposed conversion method uses 1) pitch control by playing a musical instrument and 2) noise suppression. In the pitch control, pitch patterns of music sounds played simultaneously in singing with the electrolaryx are modified so that they have specific characteristics usually observed in singing voices, and then, the modified pitch patterns are used as the target pitch patterns in the conversion from EL speech into singing voices. In the noise suppression, spectral subtraction is used to suppress the leaked excitation sounds. The experimental results demonstrate that 1) naturalness of singing voices is significantly improved by the noise suppression and 2) the pitch pattern modification is not necessarily effective in the conversion from EL speech into singing voices.