Biomedical Engineering Reference
In-Depth Information
envelope
follower
parametric
design
temporal
envelope
recorded
footsteps
spectral
envelope
white
noise
output
band pass / LPC band pass / LPC
filter
filter
Fig. 12.1
Hybrid synthesis of footstep sounds [
31
]
context: this happens e.g. in recent videogames, where the scenarios and situations
in which the game characters are engaged provide the ground parameters and the
kinematic data enabling the selection of appropriate elements of a knowledge base.
Extremely accurate collections of walking sounds exist, especially in commercial
repositories like
http://sounddogs.com
,
for creating such a dataset.
Somehow closer to an interactive synthesis paradigm, a hybrid model has been
recently proposed based on a simplified version of Cook's method, relying on the
temporal envelope control of filtered noise [
31
]. As Fig.
12.1
shows, every footstep
results by weighing the output of a series of linear filters through a temporal envelope
function. Both such filters coefficients and this function report of a characteristic
locomotion style on a specific ground material, whose sonic signature is extracted
from a set of recorded samples: the former obtained by Linear Predictive Coding of
these samples, the latter created by defining a force-dependent stochastic process on
top of the same recorded information.
The approach based on datasets or hybrid generation has fewer points when the
auditory feedback must tightly follow the locomotion and foot gestures of the walk-
ers. As we previously said, in this situation users are not passive listeners, conversely
they are engaged in a perception and action task. However in this case, also on the
light of the psychoacoustic experiments previously described, the applicability of
interactive sound rendering is necessarily limited since real walking cannot be sub-
stituted with a virtual experience, nor can the auditory cues contradict the tactile
perception through the feet. For this reason, the synthesis models which are cur-
rently receiving most attention are those capable of rendering aggregate grounds.
The related cues, in fact, can conveniently “overwrite” the feedback provided by flat
and homogeneous, sufficiently silent floors such as those covering normal buildings
and other urban spaces. For these floors, interesting augmentations can be realized
especially if companion vibrotactile cues of aggregate ground material are provided
underfoot, simultaneously with the corresponding auditory feedback.
