A Laryngographic Study on the Voice Quality of Northern Vietnamese Tones under the Lombard Effect

While acoustic changes in Lombard speech are well-documented, articulatory changes are less well-studied. This study presents recent findings of Northern Vietnamese tone production in noise from an articulatory perspective, based on laryngographic evidence of voice quality. From the time domain Lx signals, jitter and shimmer were found to decrease at higher noise levels while the mean F0 and harmonics-to-noise ratio increased. Prior hypotheses predicted that creaky tones might demonstrate different degrees of glottal vibratory changes compared to the modal tones. Interaction effects were detected between tone and noise levels, and a detailed examination showed that differences in Lombard effects were even found within creaky tones themselves. Furthermore, the laryngographic spectral tilt flattened at increasingly higher noise levels in the frequency domain. These findings point towards reduced creakiness in the voice quality of speech produced in noise, and provide evidence that hyper-articulation starts at the sound source.