Nasal Air Emission in Sibilant Fricatives of Cleft Lip and Palate Speech
Abstract
Cleft lip and palate (CLP) is a congenital disorder of the orofacial region. Nasal air emission (NAE) in CLP speech occurs due to the presence of velopharyngeal dysfunction (VPD), and it mostly occurs in the production of fricative sounds. The objective of present work is to study the acoustic characteristics of voiceless sibilant fricatives in Kannada distorted by NAE and develop an SVM-based classification to distinguish normal fricatives from the NAE distorted fricatives. Static spectral measures, such as spectral moments are used to analyze the deviant spectral distribution of NAE distorted fricatives. As the aerodynamic parameters are deviated due to VPD, the temporal variation of spectral characteristics might also get deviated in NAE distorted fricatives. This variation is studied using the peak equivalent rectangular bandwidth (ERBN)-number, a psychoacoustic measure to analyze the temporal variation in the spectral properties of fricatives. The analysis of NAE distorted fricatives shows that the maximum spectral density is concentrated in the lower frequency range with steep positive skewness and more variations in the trajectories of peak ERBN-number as compared to the normal fricatives. The proposed SVM-based classification achieves good detection rates in discriminating NAE distorted fricatives from normal fricatives.