Abstract:
Pirith is a special type of chanting; believed to be a protective doctrine preached by the Load
Buddh in Pali language. Generally, a voice signal consists of the fundamental frequency, 0
and a series of harmonic frequencies called as formants, 𝐹𝑛. As reported by several other
studies, characteristic vowels and high frequency formants are identified in chanting,
contrast to normal speaking. Hence, the motive of this study is to investigate vowel
distribution of Pirith chants and quantify voiced to unvoiced ratio utilizing computer-aided
tools. Pertaining to speech mechanism, vowels can be mapped using the relationship
between lip opening width to the first formant frequency, 𝐹1 and tongue constriction width
to the second formant frequency, 𝐹2. In this study, samples of Rathana, Karaniya Metta and
Angulimala Suttas recited by male monk chanters were recorded using high precision
microphone array and 15 samples of each Sutta were analysed. Recorded samples were then
subjected to splitting of smaller voiced segments of frame length 10 𝑚𝑠 sampling at a rate
of 44.1 𝑘𝐻𝑧. In the computational speech model, a pre-emphasis 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. Voiced to unvoiced ratio is assessed using zero
crossing rate and energy content of the acoustic signal. Results of the Voiced to Unvoiced
ratio indicates approximately 20:1, 6:1 and 14:1 for Rathana Sutta, Karaniya Metta Sutta
and Angulimala Sutta respectively. Further, the vowel distribution reveals that the majority
of vowels in Angulimala Sutta and Karaniya Metta Sutta are closer to cardinal vowel [a]
while the vowels of Rathana Sutta remains closer to cardinal vowels [u],[o],[Ɔ] and [ɒ].
