Laryngeal and tonal contrasts in the Tai dialect of Cao Bang

Voice qualities have long been thought to play an important role in tonogenetic processes by mediating the transphonologization of segments into tones (Haudricourt, 1965). Breathiness, in particular, is thought to arise as a redundant phonetic cue to onset voicing, whose subsequent loss results in new tonal categories. However, it is still unclear what role breathiness plays at a stage when tonal contrasts are fully established, but the initial laryngeal contrasts have not yet been neutralized, in part because languages that preserve this state of affairs are extremely rare.
The Tai dialect of Cao Bang (CBT), spoken in northeastern Vietnam, is just such a language. In most Tai languages, a three-tone system split into six tones following the collapse of the voicing contrast. In CBT, voicing contrasts were neutralized following loss of aspiration in initial sonorants, but are still retained in initial obstruents, along with voice quality differences most other Tai languages have lost (Hoàng Văn Ma, 1997; Pittayaporn, 2009). As a result, the six- way system only applies to a subset of the laryngeal contrasts. While breathiness can be analyzed phonologically as a redundant feature of three of these tones, its phonetic status within the tone system is still unclear. In this paper, we present the first instrumental phonetic analysis of the language. Because tone and laryngeal properties crosscut one another in this complex system, we seek to understand how these contrasts are signaled phonetically.