Emotion Recognition Using Short Time Speech Analysis - Emotional Engineering - page 98

We used a 162-dimension feature set for a complete analysis, but a remaining
point is that we did not include a feature selection procedure before the segmen-
tation. The full set of extracted features is chosen instead, and we let the seg-
mentation algorithm decide on the more appropriate segments for representing the
utterance labels. This is appropriate with respect to feature dimensions with a large
number of samples. However, the interaction between the feature selection and
segmentation approaches and its meaning will be discussed as a future issue.
6 Application for Emotion Strength Analysis
A very interesting potential application is emotion strength analysis by segment-
level speech emotion recognition. We use majority voting to decide the utterance
label (pleasure or displeasure) with the assumption that the segment label in the
majority represents the utterance label. To better understand segment labels, we
looked further into the ratio of the predicted segment labels that can represent the
strength of an utterance emotion. All speech frames are used for examining all
segments in terms of emotions.
6.1 Experimental Data
The International Affective Picture System (IAPS) [ 21 ] is used for evoking emo-
tions with different strengths. The IAPS is an emotion stimulation system built from
the results of many emotion experiments and is composed of about 1,000 pictures
labeled with a standard scale of valence (pleasure-displeasure) and arousal (excit-
ing-sleepy). Therefore, it meets our requirement for stimulating emotions with
different strengths. Figure 8 shows the four kinds of emotion strengths we de ! ned
by using the IAPS.
The experimental approach was made up of four parts in accordance with the
pleasure and displeasure emotion stimulation, which includes the de ! ned emotion
strength (weak and strong). The detailed experimental procedure is shown in Fig. 9 .
The pictures selected from the IAPS during the stimulation period were projected
on a screen to evoke emotions. Then, speech signals were collected when the
participants were reading designed scripts with their evoked emotion. The partic-
ipants were requested to close their eyes to relax during the control time. Seven
Japanese males took part in the experiment. Data were collected by using the
previously described procedures for estimating four emotional strengths and con-
tained 312 samples including 156 pleasure (78 strong, 78 weak) and 156 displea-
sure (78 strong, 78 weak) data.