The nature of left- and right-dominant sandhi in Shanghai Chinese—Evidence from the effects of speech rate and focus conditions

•The right-dominant sandhi is a phonetic reduction of the non-final tones.•The left- and right-dominant sandhis are composed of different prosodic structures.•Contrastive focus and slow speech rate are implemented through different mechanisms. This study compared the f0, duration and intensity patterns of disyllabic groups that undergo left- or right-dominant tone sandhi in Shanghai Chinese. We investigated the effects of contrastive focus and speech rate on these patterns, in order to further our understanding of the nature of left-/right-dominant sandhi and the phonetic realization mechanisms of focus encoding and speech rate. The results suggest that [Verb+Noun] phrases undergo right-dominant sandhi, which involves a phonetic reduction of the non-final tone as the f0 contour of σ1 is fully realized in focused or slow speech condition; [Adj.+Noun] compounds undergo left-dominant sandhi, which consists phonologically of rightward tone spread, since the f0 pattern of compounds is preserved in all conditions. The focus-induced adjustment patterns of f0, duration and intensity show that left-/right-dominant sandhi domains are composed of different prosodic structures and focus is indirectly encoded via prosodic structure. Although slow speech and focus both enhance the f0 realization, they are realized by way of different mechanisms. Focus is realized via a speaker's direct control of the intensity, while speech rate is realized via a speaker's intentional control of the duration, and the f0 adjustment is better regarded as the surface realization or byproduct of these adjustments.