Page 226 - Designing Sociable Robots

breazeal-79017 book March 18, 2002 14:16

Expressive Vocalization System 207

ix, yx, ih, ey, eh ow, uw, uh, oy lx, n, l, t, d, el,
eh, ah, ae, nx, yu, w, aw en, tx, dx
hx, s, z

aa, ao, ax rr, r, rx k, th, g, dh

sh, xh, ch, jh f, v iy, q

m, b, p, silence
Figure 11.6
Kismet’s mapping of lip postures to phonemes.

Kismet’s ability to lip-sync within its limits greatly enhances the perception that it is
genuinely talking (instead of being some disembodied speech system). It also contributes
to the life-like quality and charm of the robot’s behavior.
Figure 11.6 shows how the fifty DECtalk phonemes are mapped to Kismet’s lip postures.
Kismet obviously has a limited repertoire as it cannot make many of the lip movements that
humans do. For instance, it cannot protrude its lips (important for sh and ch sounds), nor
does it have a tongue (important for th sounds), nor teeth. However, computer-animated lip
synchronization often maps the 45 distinct English phonemes onto a much more restricted
set of visually distinguishable lip postures; eighteen is preferred (Parke & Waters, 1996).
For cartoon characters, a subset of ten lip and jaw postures is enough for reasonable artistic