Page 108 - Designing Sociable Robots

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The Auditory System 89

You’re a clever robot Very good Good job yes There you go
Pitch, f o (kHz)
Approvals

Hey Kismet over here Kismet Kismet look Kismet you see that
Pitch, f o (kHz)
Attentional
Bids

Bad robot Kismet don’t do that Stop it Kismet No no no
Pitch, f o (kHz)
Prohibitions

Ooh Kismet It’s gonna be okay Oh Kismet it’s okay It’s okay
Pitch, f o (kHz)
Soothings

Figure 7.3
Fernald’s prototypical prosodic contours found in the preprocessed data set. Notice the similarity to those shown
in figure 7.1.

These clustered classes were then passed to additional classification stages for further
refinement. New features had to be considered to build these additional classifiers. Using
prior information, a new set of features encoding the shape of the pitch contour was included,
which proved useful in further separating the classes.
To select the best features for the initial classification stage, the seven feature pairs listed
in table 7.2 were examined. All feature pairs worked better in separating prohibition and
soothing than other classes. The F 1 -F 9 pair generates the highest overall performance and
the least number of errors in classifying prohibition. Several observations can be made
from the feature space of this classifier (see figure 7.4). The prohibition samples are clus-
tered in the low pitch mean and high energy variance region. The approval and attention
classes form a cluster at the high pitch mean and high energy variance region. The soothing