When in a noisy environment speakers modify their speech production by increasing loudness, vowel duration, and fundamental frequency (F0), a phenomenon known as Lombard speech. Here Lombard speech in Thai was investigated in order to determine the effects of noise on the realisation of F0 in Thai lexical tones. Analysis of the acoustic characteristics of the five Bangkok Thai tones, in both continuous speech and citation form, produced in noise and in quiet showed that F0 is heightened in Lombard compared with clear speech. In addition, generally the contour of the tones also changes in Lombard speech; contours tend to be exaggerated towards the end of the tone in a direction consistent with the contour of the tone.
Bibliographic reference. Kasisopa, Benjawan / Attina, Virginie / Burnham, Denis (2014): "The Lombard effect with Thai lexical tones: an acoustic analysis of articulatory modifications in noise", In INTERSPEECH-2014, 1717-1721.