Glottalized and nonglottalized tones under emphasis: open quotient curves remain stable, F0 curve is modified

Tones B2 and D2 of Hanoi Vietnamese have strongly contrasting voice quality features: tone B2, which is glottally constricted, is here compared with a similar but nonconstricted tone (tone D2). Under emphasis, the slope of F0 curves is increased and/or F0 register is raised. The open quotient values (calculated from the derivative of the electroglottographic signal, which has been shown to yield very accurate values) do not vary significantly with emphasis. A description in terms of curve amplification is put forward. As for changes in length, they appear to be speaker-dependent.