dimensional attributes:
width (individual/ensemble/room/scene)
distance (individual/ensemble/room/scene)
depth (individual in special cases/ensemble/
room/scene)
direction (individual/ensemble/room/scene)
immersive attributes:
envelopment (environmental/source-related)
presence
Every level of organization within the scene can be
characterized by the dimensional attributes, but only
certain situations give rise to envelopment and presence.
3. ELECTROACOUSTIC MUSIC
3.1 Spatial Attributes, Scene Analysis and Auditory
Spatial Schemata
Up to this point we have described a nested organization
for scene analysis that is based in acoustic music.
Rumsey's framework of source/ensemble/room/scene is
intended for the subjective evaluation of the audio
reproduction of music recordings. And, while the
content of electroacoustic music can be quite dissimilar,
the notion of nested levels of organization from micro to
macro would appear to be quite valid for almost every
kind of music. Rumsey's focus on typical audio content
though complicates his framework in a way that
inadvertently undermines the notion of a simple microto-macro organization. The shift from 'ensemble' to
'room' is not just a shift to the next higher level of
nesting; it is a categorical shift that is normative only in
the domain of acoustic music where instruments are
indeed enclosed in rooms.
There are two issues revealed when considering
the concept of 'room' in the context of electroacoustic
music. The first issue is that the 'room' or the
simulation of the 'room' can be accomplished by the
treatment of an acoustic signal with a reverberator.
Since the output of the reverberator is essentially a dense
ensemble of duplicated signals, we have to ask why the
'room' is not considered a type of 'ensemble',
essentially just another level of nesting in the
organization? Then too, in the case that the original
source signal is omitted, the reverberator's output itself
essentially becomes a potential source. What then is the
essential difference between a source, an ensemble and a
room? The answer comes in response to the second
issue. A 'room' is something different from a type of
acoustic signal or treatment of a signal: it is an
understanding that the listener constructs in response to
auditory experience. 'Room' is part of our cognitive
understanding formed in relation to auditory spatial
schemata. Depending on the circumstances, 'room' may
or may not be invoked by the listener in the process of
forming an understanding of the auditory scene. In some
circumstances we can imagine that 'room' is automatic
and akin to schema-based stream segregation [3]. In
other circumstances 'room' might well be an inference
based on incomplete or fragmentary acoustic
information. It is not the perceived nested relationships
that determine the categories.
In response to the concept of 'room' presented by
Rumsey [15], we have disentangled a confluence of
terminology created by mixing the immediate and
tangible spatial organization with patterns of spatial
understanding. First, we have recognized that 'room' is
not inherently a level in nested spatial relationships.
Second, we have connected 'room' to the listener's
cognitive spatial understanding and auditory spatial
schemata. The original sense of the distinctions between
source, ensemble and room has faded away. ('Source'
and 'ensemble' are also discussed below in relation to
auditory spatial schemata.) So, what remains of the
original concept of a nested organization of spatial
relationships? Clearly, the listener's perception of nested
spatial relationships depends on the tangible
circumstances, the particulars of the auditory scene. For
electroacoustic music the elements in the nested
structure are not limited a priori to one set of relational
categories. At times, there may be no clear boundary
between source and ensemble, that is, between one and
many sources. A full description of spatial content and
its implications within an artistic context may be very
complex. Auditory spatial schemata may be stretched or
even violated. Our ability to describe and categorize
these complex interactions depends on having clear
concepts and terminology so that we can recognize the
crisscrossing of boundaries and the disruption of spatial
norms in the artistic interplay.
3.2 Spatial Schemata and Audio Reproduction
Auditory spatial schemata are the recurrent patterns by
which we understand the behavior of sound in space.
All of our sensory capacities contribute to forming our
core spatial schemata [7] and, therefore, auditory spatial
schemata can be largely understood as projections of
multimodal spatial schemata within the auditory domain.
The listener makes sense of spatial sound first and
foremost in terms of spatial schemata that are learned
and reinforced in everyday life. The general schema of
OBJECT gives rise to the auditory schema of SOURCE.
The general schema of COLLECTION gives rise to
ENSEMBLE. Both possess spatial attributes and typical
spatial behaviors.
Sound localization is generally recognized as
having a weak influence on the auditory scene. For that
reason, spatial schemata have a particularly important
role in spatial hearing because the schemata give
coherence to spatial information that may otherwise be
faint or incomplete. Spatial schemata are particularly
important for audio reproduction when no other sensory
information may collaborate the auditory spatial content.
Our spatial schema for PATH gives coherence to motion
effects that can otherwise be quite fragile. The listener
makes sense of spatial relationships and creates a spatial
organization. Then too, the disembodied sound of audio
reproduction is often interpreted in a framework that is
specific to this context. For example, the spatial
arrangement of sources in a typical stereo pop song
makes no physical sense. We accept the spatial
arrangement as an idiom of audio reproduction, a
musical-spatial idiom. The immaterial nature of audio
reproduction enables auditory spatial art to exploit the
spatial schemata of everyday life.
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