Biomedical Engineering Reference
In-Depth Information
FIGURE 7-24
Tactile display
technologies and
interaction. [Adapted
from (Pasquero
2006)], with
permission.
Several features of vibrotactile stimuli can be modulated to convey information over
this sensory channel (Cincotti, Kauhanen et al., 2007). The list can be divided into two
subsets. The first includes features related to physical perception and are as follows:
•
Frequency
: the main spectral component of the periodic stimulus
•
Intensity
: the amplitude of stimulation (measured either as force applied or as
displacement produced)
•
Timbre
: the complexity of the stimulation waveform (i.e., the content of harmonics
in the spectral representation)
•
Duty cycle
: the ratio of the durations of the on and off time on an elementary
stimulation
•
Spatial location
: the body part or the pattern of parts that are stimulated
Features in the second subset are clearly perceived by an individual but do not rely on any
specific property of the receptors. They need to be interpreted on a cognitive level:
•
Rhythm
: the sequences of stimulation and pauses, with specific durations, that
compose the current message (i.e., a triplet of stimuli such as a Morse coded SOS)
•
Tempo
: the speed, due to longer or shorter duration of the whole message, given at
fixed rhythm
•
Flutter
: an amplitude modulation of the stimulation carrier frequency that can either
be perceived as increase and decrease of the intensity (if modulation is slower than
5 Hz) or as “roughness” (if modulation is faster than 10 Hz)
