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with respect to time using an accurate statistic law that can be controlled. A global
control of the
fire intensity, mapped with the control of the grain generation
(amplitude and statistic law), is then designed. A rainy weather sound ambiance can
be designed with a rain shower, water
flow and drops, each of these environmental
sounds being independently spatialized and constructed from a combination of the
previous grains (see Verron et al.
2009
for more details). In case of interactive uses,
controls can be achieved using either MIDI interfaces, from data obtained from a
graphical engine or other external data sources.
4.5
Evidence of Semiotics for Non-linguistic Sounds
To propose an even more intuitive control of sound synthesis that directly uses a
BCI, a relationship between the electroencephalogram (EEG) and the nature of the
underlying cerebral processes has to be investigated. We here present results of
several experimental studies aiming at supporting the existence of semiotics for
non-linguistic sounds. In these studies, we used either synthetic stimuli using
analysis/transformation/synthesis processes or sounds of a speci
c kind called
“
'
responses and reaction times (RTs) provided objective measurements to the pro-
cessing of stimulus complexity.
Electrophysiological data
abstract
”
sounds promoting acousmatic listening (cf. Sect.
4.2
). The participants
: When appropriate, we also investigated the neural
bases of the involved brain processes by analysing the EEGwith the method of event-
related potentials (ERP) time-locked to the stimulus onset during the various infor-
mation processing stages. The ERP elicited by a stimulus (a sound, a light, etc.) are
characterized by a series of positive (P) and negative (N) de
ections relative to a
baseline. These de
ned in terms of their polarity,
their maximum latency (relative to the stimulus onset), their distribution among
several electrodes placed in standard positions on the scalp and by their functional
signi
ections (called components) are de
cance. Components P100, N100 and P200 are consistently activated in
response to the auditory stimuli (Rugg and Coles
1995
). Several late ERP compo-
nents (N200, P300, N400, etc.) are subsequently elicited and associated with specific
brain processes depending on the experimental design and the task in hand.
4.5.1 Perceptual Categorization of Sounds from Impacted
Materials
In this experiment, we studied the perception of sounds obtained from impacted
materials, in particular, wood, metal and glass (Aramaki et al.
2010
a; Aramaki et al.
2010
b; Aramaki et al.
2011
). For this purpose, natural sounds were recorded,
analysed, resynthesized and tuned to the same chroma to obtain sets of synthetic
sounds representative of each category of the selected material. A sound-morphing
process (based on an interpolation method) was further applied to obtain sound
continua simulating progressive transitions between materials. Although sounds
