Recognition of Vowels for Sri Lankan Traditional Pirith Chanting Using Formant Variation

Abstract

Pirith is believed to be a doctrine preached by Lord Buddha and regarded to obtain protection from evil, promote health and well-being. Voice source produces a harmonic series, consisting of the fundamental frequency, F0 and harmonic frequencies called as formants, Fn. Vowels can be mapped using the relationship between lip opening width to the first formant frequency, F1 and tongue constriction width to second formant frequency, F2. This work is dedicated to developing phonetic picture on Pirith chants and analyze acoustic properties using computer-aided tools. As reported by several other studies, characteristic vowels and high frequency formants are identified in chanting in contrast to normal speaking. The motive of this study is to investigate vowel distribution of Pirith chants with the aim of special pattern recognition. Samples of Ratana, Karaneeya and Angulimala Suttas recited by male monk chanters were recorded using high precision microphone array and 15 samples of each Sutta were analyzed. Recorded samples were then subjected to splitting of smaller voiced segments of frame length 10 ms using sampling rate of 44.1 kHz. In the computational speech model, a preemphasis filter is applied to the sampled time series of voiced segment to cancel out the effect of glottis. Then frame-by-frame analysis was used with hamming windows and liner predictive coding (LPC) and auto correlation to extract the formant values. The vowel distribution reveals that a higher number of open vowels are articulated in Pirith chanting with totally disuse of closed vowels.