THE ARTISTIC PLAY OF SPATIAL ORGANIZATION:
SPATIAL ATTRIBUTES, SCENE ANALYSIS AND
AUDITORY SPATIAL SCHEMATA
Gary S. Kendall
Northwestern University
Music Technology Program
Evanston, IL 60208 USA
[email protected]
ABSTRACT
Electroacoustic music lacks a definitive vocabulary for
describing its spatiality. Not only does it lack a
vocabulary for describing the spatial attributes of
individual sound sources, it lacks a vocabulary for
describing how these attributes participate in artistic
design and expression. Following work by Rumsey [15]
the definition of spatial attributes is examined in the
broader context of auditory scene analysis. A limited
number of spatial attributes are found to be adequate to
characterize the individual levels of organization nested
within the auditory scene (levels that for acoustic music
Rumsey labels as source, ensemble, room and scene).
These levels are then viewed as products of both tangible
spatial relationships and auditory spatial schemata, the
recurrent patterns by which listeners understand the
behavior of sound in space. In electroacoustic music the
interrelationship of spatial attributes and spatial
schemata is often engaged in a play of perceptual
grouping that blurs and confounds distinctions like
source and ensemble. 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 violation of
conventions in this artistic interplay.
1. INTRODUCTION
The expanded range of its spatial palette is one of the
important features that distinguish electroacoustic music
from acoustic music. The situation for spatiality in
electroacoustic music is similar to that for sound
synthesis in the sense that the experience of the natural
world provides an inspiration for creativity and research.
At the same time technology enables new possibilities
that reach beyond the bounds of everyday experience.
Electroacoustic music's capacity to manipulate audio
signals creates a context in which there can be uniquely
complex interactions between spatial hearing and other
domains of perception and cognition. This is especially
true when electroacoustic composers play with the
fundamentals of spatial organization in music by
manipulating perceptual grouping and violating spatial
schemata. Spatial audio, and especially spatial audio for
electroacoustic music, is an artistic domain that often
throws the spatial conventions of the natural world into
relief by distorting or violating them. In order to
appreciate the crisscrossing of boundaries and
conventions in this artistic interplay, our concepts and
vocabulary should be in good alignment with the
listener's perceptual and cognitive processes.
2. TERMINOLOGY
2.1 The Problem of Terminology
While the spatiality of acoustic music, even 20th century
acoustic music, can be discussed in commonly
understood terms [5], the spatiality of electroacoustic
music still lacks a definitive vocabulary. When music is
performed by acoustic instruments in an acoustic
environment, the physical level of description by itself
often provides a workable roadmap to both the listener's
experience and the composer's intent. We have a wealth
of shared experiences and traditions of acoustic
performance despite the perceptual complexity and
individuality of many performances. In electroacoustic
music, the acoustic experience has often been a reference
point, but the technology of electronic reproduction
expands the scope and complexity of spatiality in a
radical way. Even though the apparatus may be located
within a physical space and even though our spatial
hearing has developed within a physical world,
electronic reproduction creates the potential for an art of
spatiality. Consider how the experience of a diffuse
granular cloud [21] emerges from the details of the
granular synthesis or how the experience of spectral
bands distributed in space challenges [20] our notion of
what constitutes a 'source.' Electroacoustic music
hardly has the vocabulary to describe the scope of spatial
possibilities or to explain the relationship of signal
processing techniques to the listener's perceptions.
Recent perceptual research can help us begin to
clarify our vocabulary. A great deal of relevant research
has emerged from the study of spatial impression
associated with subjective acoustics of concert halls [2].
In the subjective acoustics of electronic reproduction,
Zacharov and Koivuniemi [22] and Rumsey [16] provide
in-depth discussions and classification of perceptual
spatial attributes. One particularly important area of
focus has been the interrelated study of apparent source
width and listener envelopment [1, 4]. These perceptual
qualities have been studied almost exclusively in the
context of concert hall acoustics and more recently in the
context of sound reproduction, especially in surround
sound systems. And, while there is much that can be
gleaned from this research, the difference between the
contexts considered in the aforementioned research and
the context for electroacoustic music is profound. For
one thing, concert hall acoustics and reproduced sound
are often partitioned conceptually into direct sound,
indirect reflections and reverberation. This is reflected
in a terminology that can be parsed into terms relating to
the source and those relating to the environment.
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