Characteristics of clear and vocoded Persian vowels and their preliminary comparison with English vowels

Vowel perception occurs through the spectral and temporal information transference. Presence of temporal information in the envelope makes the speech signals perceivable, even when spectral information weakens in the synthesized signals. The present study deals, for the first time, with determining and comparing the acoustic characteristics of clear and vocoded vowels of the speakers of English and Persian languages. Ten native Persian (5 female and 5 male) and one male native English speakers produced their simple vowels of their mother tongue for three times. Tokens were of 180 Persian and 24 English phonetic samples. The vowels were then vocoded using MATLAB software and 270 Persian Vocoded samples and 54 English Vocoded samples were extracted. The waveforms, spectrograms and LPC diagrams of clear and vocoded vowels were analyzed using the Praat software. Results showed that in Persian speakers F0, F1, vowel space and duration of clear vowels were higher for females than males but the intensity was lower. Formant frequencies for F1-F3 were different across two languages. Vowel space was greater in Persian and English vowels duration and intensity were longer and lower respectively. In both languages, F0 and formants of vocoded vowels were not identifiable, and their LPC diagrams had rounded peaks with lower amplitudes. Duration of clear and vocoded vowels was similar, but intensity of the latter decreased in Persian and enhanced in English. Results showed spectral differences between vocoded and clear vowels in both languages.