Analysis of detection of vowel offset point for coded speech

Vowel onset and vowel offset points are the instants at which the onset and offset of vowel take place in the speech signal. Vowel regions start with the vowel onset point and end with the vowel offset point. This paper discusses the effect of speech coding on detection of vowel offset point. Speech coding is the one of the major degradation in mobile environment. In this work, effect of speech coding is studied by using two recently developed methods, COMB-ESM and SE-GC for vowel offset point detection. COMB-ESM method uses the combination of evidences from excitation source, spectral peaks energy and modulation spectrum. SE-GC method uses spectral energy within glottal closure region for detecting the vowel offset points. Speech coders used in this study are GSM full rate (ETSI 06.10), CELP (FS-1016), and MELP (TI 2.4 kbps). Performance of vowel offset point detection methods is evaluated using TIMIT database and consonant-vowel (CV) units collected from the broadcast news corpus. Experimental results show that performance of the SE-GC method is better compared to COMB-ESM method under speech coding.