An articulatory study of emotional speech production

Few studies exist on the topic of emotion encoding in speech in the articulatory domain. In this report, we analyze articulatory data collected during simulated emotional speech production and investigate differences in speech articulation among four emotion types; neutral, anger, sadness and happiness. The movement data of the tongue tip, the jaw and the lower lip, along with speech, were obtained from a subject using an Electromagnetic articulography (EMA) system. The effectiveness of the articulatory parameters in emotion classification was also investigated. A general articulatory behavior observed was that emotionally elaborated speech production exhibits more peripheral articulations when compared to neutral speech. The tongue tip, jaw and lip positioning become more advanced when emotionally charged. This tendency was especially prominent for the tongue tip and jaw movements associated with sad speech. Angry speech was characterized by greater ranges of displacement and velocity, while it was opposite for sad speech. Happy speech was comparable in articulation to the neutral speech, but showed the widest range of pitch variation. It, however, remains to be seen if there is a trade-off between articulatory activity and voicing activity in emotional speech production. Multiple discriminant analysis showed that emotion is better classified in the articulatory domain. One probable reason is that the independency in the manipulation of each articulator may provide more degrees of freedom and less overlap in the articulatory parameter space. Analysis also showed distinct emotion effects for different phonemes: the high front vowel /IY/ was found to be less discriminated in both articulatory and acoustic domains than other peripheral vowels such as /AA/ and /UW/. It is likely that the physical boundary effect in the /IY/ articulation may leave less room to vary the tongue positioning and/or the lip configuration when compared to other vowels, resulting in less acoustic contrast among emotion types.