Abstract
This research explores the crucial role of spatialisation within electroacoustic composition through a detailed analysis of a section of the author's work 'Motion', composed in 5th order Ambisonics for hemispheric loudspeaker arrays. It focuses in particular on how spatial analysis tools can reveal perceptual relationships that traditional spectral analysis alone cannot adequately capture. While spectral analysis provides invaluable insight into timbre and frequency content, it cannot show the dynamic interplay of sound sources in a three-dimensional environment. As spatialisation profoundly influences how listeners perceive individual sound events, their interactions and the overall coherence of a composition within a given acoustic space, the analysis of it is even more important.
The author also draws on the importance of analysing spatialisation to provide insights that are otherwise not easily understood. One of the many challenges faced by a composer working with multichannel audio is the uncertainty of the actual loudspeaker configuration of the concert space. A spatial analysis of immersive electroacoustic works can provide insights into how these problems can be addressed through compositional decisions based on auditory perception. Such analysis can help composers to anticipate potential problems arising from different room acoustics or listener positions, ultimately leading to a more consistent and effective listening experience in different venues.
Linked to this, the research provides an overview of auditory perception within hemispheric reproduction systems, building on Kendall's framework that "listeners experience electroacoustic music as full of meaning and significance, and they experience spatiality as one of the factors contributing to its meaningfulness". Drawing on Bregman's auditory scene analysis, specifically stream segregation, the analysis thus focuses on how spatial techniques can address masking effects through spatial separation, as discussed also in Brümmer's work on the decomposition of sound material through spatialisation.
By combining multiple analytical perspectives in the form of spectral analyses, contextualised with spatial analysis tools, this research aims to provide new insights into the relationship between spatial composition and auditory perception in contemporary electroacoustic composition, contributing to the growing body of knowledge on spatial perception and compositional practice in immersive audio environments.
Introduction
In this exposition, I will address the following artistic research question: What insights can be gained from a spatial analysis of an immersive electroacoustic composition? As this question is quite broad, I will focus on auditory perception, specifically with regard to the psychoacoustics of immersive audio in a hemispherical loudspeaker array.
Having conducted a number of experiments investigating different analysis and visualisation methods, I selected a specific combination of frequency analysis and spatialisation visualisations. Section 3 will show the combined visualisation of different parts of a composer's work.
A spatial analysis has been conducted on an electroacoustic work titled "In Motion", which was composed in 7th order Ambisonics. In this composition, I highlight a number of different spatial motions and their impact on auditory perception. At the beginning of the piece, I demonstrate perceptual issues in localising certain sounds and explore various solutions to aid the listener in perceiving the spatial movements. Spatial composers need a good understanding of psychoacoustics, particularly with regard to hemispherical loudspeaker arrays, which are common in Ambisonics fixed media concerts. Only by considering the specifics of human auditory perception during the compositional process can the composer's intention be conveyed to the listener.
As these compositional decisions are based primarily on perception, they can only be fully experienced through listening. Nevertheless, I would like to investigate to what extent it is possible to demonstrate these decisions using visualisation methods. This could also help to further understanding of different spatial electroacoustic compositions. This research therefore aims to provide an overview of the various possibilities for spatial analysis, as well as their limitations and opportunities.
The exposition and the embedded research is based on a number of academic and artistic references, a few of them I would like to highlight here.
In "Auditory scene analysis: the perceptual organization of sound" Albert S. Bregman established the phenomenological foundation of auditory perception. In my investigation, I'll draw from it several times, especially in regard to 'Stream Segregation Based on Spatial Location' [Bregman, 2006].
Building upon the work of Bregman are among many others the academic contributions of Gary Kendall who developed a more concrete framework of spatial perception in works such as "The Artistic Play of Spatial Organization: Spatial Attributes, Scene Analysis and Auditory Spatial Schemata" and "Spatial Perception and Cognition in Multichannel Audio for Electroacoustic Music" [Kendall, 2007, 2010].
In "Space-form and the acousmatic image" Denis Smalley coined the expression "Sounds in general, and source-bonded sounds in particular, therefore carry their space with them – they are space-bearers." [Smalley, 2007]. This remark opens the interesting discussion, how far potential movements are already embedded in sounds, if they, according to Smalley already 'carry their space with them'. This is a very important discussion, as highlighted by Natasha Barret: "A state of conflict will arise where the spatial information inherent to each sound-object is conflicting with their 3D spatial dispositions. Conflict can arise when opposing spatial allusions are juxtaposed, even though the material may conform to the same spatial illusion. The 3D spatial clarity prevents the opposing allusions collapsing into one single allusion or even departing into a new realm of fantasy." [Barrett, 2002].
More direct references to my own investigation I found in works by Catena, e.g. "Concepts and approaches in analysing spatial sound movements: a link between Mozart and acousmatic music" and "Missing memories: why we need to analyse and notate spatialisation" [Catena, 2022, 2024].