Acoustic Analysis of Taiwanese Tones in Esophageal Speech and Pneumatic Artificial Laryngeal Speech

Purpose: This study examined the acoustic properties of Taiwanese (Southern Min) lexical tones produced in esophageal speech (ES) and pneumatic artificial laryngeal speech (PAL), including onset fundamental frequency (F0), slope of F0 contour, duration, and amplitude (intensity) of the vowel portion of syllables carrying seven Taiwanese tones. Method: Seven ES speakers, seven PAL speakers, and 18 normal laryngeal (NL) speakers (all male) read aloud target syllables carrying the tones in monosyllables, disyllables, and sentences. Acoustic features were measured with Praat. Results: Acoustic analysis revealed (a) no significant effects of linguistic level on acoustic parameters except for duration, which generally significantly decreased from monosyllables to disyllables to sentences for Tones 1 and 5; (b) significant differences across the speaker groups in onset F0 (PAL > ES > NL), duration (PAL > NL and PAL > ES for all tones), and mean amplitude (PAL > NL > ES); and (c) no significant difference in mean slope of F0 contour across the speaker groups. Conclusions: These preliminary data on acoustic properties of Taiwanese tones produced by ES and PAL speakers could facilitate the design of therapeutic strategies for improving the intelligibility of alaryngeal lexical tones. Further studies are recommended to examine the relative perceptual importance of the acoustic parameters.