Modification of misarticulated fricative /s/ in cleft lip and palate speech

Abstract

Cleft lip and palate is a craniofacial condition that affects the intelligibility of speech. The current work describes a modification of three types of misarticulated fricative /s/ in cleft lip and palate speech, which include palatalized /s/, phoneme-specific nasal air emission distorted /s/, and glottal stop substituted /s/. By using the knowledge of the glottal activity, frication, and silence, an approach is proposed for misarticulated fricative detection and categorization of the type of error. Based on the category of error, an appropriate modification technique is applied. The deviations of palatalized /s/ and phoneme-specific nasal air emission distorted /s/ are corrected by modifying the spectral energy. The high-frequency energy levels are emphasized to improve the perception of fricative /s/ using spectral tilt modification. Glottal stop substitution is modified by inserting artificially synthesized /s/, where the fricative /s/ signal is synthesized using white noise signal and linear prediction filter obtained from normal children fricative /s/. Further, the modified speech samples are subjected to objective and subjective evaluation. The evaluation scores obtained from objective and subjective assessment indicate speech intelligibility improvement of the modified signals compared to the misarticulated fricative /s/.