# How Much Does the Dynamic F0 Curve Affect the Expression of Emotion in Utterances?
## 4 Discussion
### Discrepancies with Previous Literature  
In our analysis, as illustrated in Figures 5 and 6, we observed that anger, disgust, and fear all exhibit downward pitch contours at elevated pitch levels. Emotions such as sadness, calm, and neutral are characterized by downward pitch contours at subdued pitch levels. Notably, sadness occurs at a slightly higher pitch level than calm and neutral, which might reflect a difference in emotional arousal. The similarity between the pitch contours of calm and neutral suggests that these two emotions may be challenging to distinguish for listeners, potentially leading to misclassification. This difficulty underscores the importance of nuanced acoustic analysis in emotion recognition systems. Among these emotions, anger starts at a higher pitch level than both disgust and fear, aligning partially with [8]'s findings regarding anger's high pitch. While disgust also shows a downward contour similar to anger, it displays more fluctuation in the pitch contour compared to fear. To further examine the nuances between anger and disgust, we present the modeled F0 contours for these emotions in Figure 7. As depicted in the left panel of Figure 7, both emotions demonstrate very similar shapes in their dynamic F0 movements, indicating a shared downward trajectory in pitch over time. However, the anger emotion (red line) consistently exhibits higher pitch levels compared to disgust (blue line) throughout the utterance. Figure 7: Comparison of pitch contours between angry (red) and disgust (blue) speech samples. The **left panel** displays the fitted pitch values in semitones over 500 samples, with shaded areas representing the confidence intervals, excluding random effects. The **right panel** shows the estimated difference in the F0 (fundamental frequency) between the angry and disgust conditions, with the shaded area indicating the confidence interval of the difference. The right panel of Figure 7 illustrates the estimated difference in the F0 between the angry and disgust conditions, along with the confidence interval of the difference. This visual comparison highlights that while the dynamic patterns of pitch movement are similar for both emotions, the overall pitch level serves as a distinguishing feature. The elevated pitch levels associated with anger support the notion of increased arousal and intensity in this emotion, which is reflected acoustically. Interestingly, disgust in our data does not conform to the low mean pitch reported previously. In [8], disgust is expressed with a low mean pitch, a low intensity level, and a slower speech rate than the neutral state does. However, this is not the case in our data. Instead, it displays elevated pitch levels with more fluctuation in the pitch contour compared to fear. This discrepancy suggests that disgust may be expressed differently in the RAVDESS dataset, potentially due to cultural, linguistic, or methodological differences. The expression and perception of emotions can vary across cultures and languages. What is considered a typical acoustic manifestation of an emotion in one culture may differ in another. Or it can be the case that the actors in the RAVDESS dataset may have employed a different vocal strategy to convey disgust, perhaps emphasizing certain prosodic features to make the emotion more discernible. Methodological differences may have led to the differences in the finding; our use of dynamic modeling with GAMMs allows for capturing temporal variations in pitch contours that static measures like mean pitch may overlook. The acoustic properties of calm and sadness emotions are characterized by downward pitch contours at subdued pitch levels, reflecting their low arousal states. This downward trajectory in pitch aligns with previous research indicating that lower pitch and reduced variability are common in less active or more negative emotional states. However, there are notable differences between the two emotions. Sadness consistently exhibits a slightly higher pitch level than calm throughout the utterance.