Computation of L2 speech rhythm based on duration and fundamental frequency

Rhythmic characteristics of speech vary between native and non-native speakers. Studies comparing the rhythmic properties of L1 and L2 speech based on rhythm metrics have shown that this relationship is far from straightforward. It seems evidently the case that the difference between native and non-native speech is a complex interaction of a variety of rhythmic cues (duration, F0 and intensity). In this study we extended the durational domain by F0 and tested whether metrics combining duration and F0 (henceforth combined measures) could better account for the rhythmic differences between L1 and L2 speech. To test this, 5 native Mandarin speakers and 5 Italian learners of Mandarin recorded The North Wind and the Sun in Mandarin. Besides, each Italian speaker also recorded the same text in Italian. Each sentence in L1-L2 Chinese and in L1 Italian was segmented into syllables. We calculated duration- and F0-based metrics (Δsyllable duration/F0; r-PVI syllable duration/F0; Varco syllable duration/F0; nPVI syllable duration/F0), as well as combined metrics (Δcombined, Varco combined, rPVI combined and nPVI combined). Results show that measures taking syllable duration and F0 separately do not differentiate consistently between L1 and L2 Chinese, while combined metrics reflect more systematically the variability pattern between L1 and L2 Chinese speech rhythm. More research is, however, needed to explore the significance of combined metrics as opposed to duration- and F0-based measures for the perceived rhythmic differences between L1 and L2 speech.