Page 212 - Designing Sociable Robots

breazeal-79017 book March 18, 2002 14:16

Expressive Vocalization System 193

• Breathiness Controls the aspiration noise in the speech signal. It adds a tentative and
weak quality to the voice, when speaker is minimally excited. DECtalk breathiness and
lax-breathiness vary directly with this.

• Brillance Controls the perceptual effect of relative energies of the high and low frequen-
cies. When agitated, higher frequencies predominate and the voice is harsh or “brilliant”.
When speaker is relaxed or depressed, lower frequencies dominate and the voice sounds
soothing and warm. DECtalk’s richness setting varies directly as it enhances the lower
frequencies. In contrast, DECtalk’s smoothness setting varies inversely since it attenuates
higher frequencies.

• Laryngealization Controls the perceived creaky voice phenomena. It arises from minimal
sub-glottal pressure and a small open quotient such that f 0 is low, the glottal pulse is narrow,
and the fundamental period is irregular. It varies directly with DECtalk’s laryngealiza-
tion setting.

• Loudness Controls the amplitude of the speech waveform. As a speaker becomes aroused,
the sub-glottal pressure builds which increases the signal amplitude. As a result, the
voice sounds louder. It varies directly with DECtalk’s loudness setting. It also influences
DECtalk’s gain-of-voicing.
Pause Discontinuity Controls the smoothness of f 0 transitions from sound to silence for
•
unfilled pauses. Longer or more abrupt silences correlate with being more emotionally
upset. It varies directly with DECtalk’s quickness setting.

• Pitch Discontinuity Controls smoothness or abruptness of f 0 transitions, and the degree
to which the intended targets are reached. With more speaker control, the transitions are
smoother. With less control, they transitions are more abrupt. It contributes to DECtalk’s
stress-rise and quickness settings.

Articulation
The autonomic nervous system modulates articulation by inducing an assortment of phys-
iological changes such as causing dryness of mouth or increased salivation.

• Precision Controls a range of articulation from enunciation to slurring. Slurring has mini-
malfricationnoise,whereasgreaterenunciationforconsonantsresultsinincreasedfrication.
Strongerenunciationalsoresultsinanincreaseinaspirationnoiseandvoicing.Theprecision
of articulation varies directly with DECtalk’s gain-of-frication, gain-of-voicing,
and gain-of-aspiration.