Acoustic Analysis of Oral and Nasal Speech of Normal versus Cleft Lip and Palate

Analysis of acoustics and speech is an important prerequisite to understanding of speech perception of an individual. Nasal and oral sounds have to be understood clearly to understand speech effectively. The present study was aimed at finding the severity of nasal and oral sounds of cleft lip and palate by comparing normal speech sounds and the speech of cleft lip and palate subjects. Speech is an acoustic signal which results from three components of voice production: voiced sound, resonance, and articulation. Acoustic resonances in the vocal tract can produce peaks in the spectral envelope of the output sound. In speech science, the word ‘formant’ is used to describe either the spectral peak or the resonance that gives rise to it. These formant frequencies are obtained from Welch’s power spectral density estimate method using MATLAB. Statistical significance test is carried out to compare the speech of both normal and CLP subjects. The results of the statistical analysis are utilized to find the severity in CLP. The speech samples of different Kannada syllables of normal as well as cleft lip and palate subjects are used. Eight oral and two nasal syllables of seven normal and seven abnormal persons are used and compared. These helps in classifying the severity of speech disorder as mild, moderate, moderately severe and severe. This provides information about atypical consonant productions, abnormal nasal resonance, abnormal nasal airflow, altered laryngeal voice quality, nasal or facial grimaces and velopharyngeal dysfunction which helps in speech therapy and speech intelligibility.