The Effect of Fundamental Frequency on Mandarin Intelligibility by L2 Learners in Quiet and Noise Environments: A Pilot Study

Fundamental frequency (F0), listening environment, and semantic context are three important factors for both tonal and non-tonal language intelligibility by native speakers. However, it remains unclear how these factors affect second language (L2) learners of Mandarin Chinese and whether there are differences between native and L2 Mandarin speakers. Through speech re-synthesis and sentence counterbalancing, this study investigated the possible effects of F0 (i.e., natural F0 versus flattened F0) on the intelligibility of Mandarin speech by L2 Mandarin learners from different proficiency levels in quiet and white noise conditions when controlling for sentence context. A mixed-effect statistical model confirmed the main effects of F0 contour, listening environment, and proficiency level. That is to say, the lack of natural F0 contour, the presence of noise, and the lower proficiency level would predict the reduction in intelligibility when adjusting for the other two variables. However, no significant interactions were found. Specifically, the hypothesis that flattened sentences are as intelligible as natural sentences for more advanced learners was not supported due to the change of experimental subjects from native speakers to L2 speakers. It was proposed that compared to native speakers, L2 speakers’ underdeveloped utilization of secondary cues and semantic contexts, due to a developing proficiency level, may lead to non-significant interactions. The finding of the effect of F0 on intelligibility also illustrates the importance of tone accuracy and diversifying L2 learners’ linguistic input in Chinese pronunciation teaching and learning.