# Evaluation of Three Auditory-Sculptural Qualities Created by an Icosahedral Loudspeaker
## 1 Introduction  
In spatial audio technology, see e.g., [1], a virtual source is a model description of how technical parameters map to the characteristics of an isolated auditory event. Most of all characteristics, the virtual source describes the relation of a modeled auditory event location to the gains and delays that feed a signal to the surrounding loudspeakers, as the most common application. In acoustically treated studio environments [2], numerous effects can be controlled relatively precisely on the level of abstraction of such a single, moving virtual source for spatialization. A common mechanism utilized is summing localization [3], which fuses the multiple sound instances of the loudspeakers to clearly localized auditory events whenever sounds are arriving with time lags \(<1\) ms.  
Spatialization that creates immersive sound environments in electroacoustic music with 3D surround loudspeaker systems [4] often employs particle systems of virtual sources [5, 6] fed by spectrally modified sounds. In contrast to isolated auditory events, we use the term auditory object [7] to refer to what perception segregates from a mixture of multiple concurrent sounds. [PERSON] [8] argues that auditory objects and constellations thereof are only indirectly controlled by spatialization using virtual source constellations because auditory objects are not only subject to the precedence effect [9, 10], but also many other psychoacoustic effects, e.g., masking, auditory grouping, auditory attention, etc. [11]. Only in exceptional cases, all intended and composed virtual source constellations can become fully transparent auditory objects for all listeners. What frequently turns out to be effective in spatial electroacoustic music is to make spatialization time-variant and to make its virtual sources move along trajectories that [PERSON] refers to as gestures [12]. The knowledge about the effectiveness of spatial gestures is particularly helpful, as discussed by [PERSON] and [PERSON] [13, 14]. Such time-variant spatializations often offer comprehensible and stable auditory impressions that can be perceived by many listeners throughout the audience, even with a manageable number of loudspeakers and signals. Beamforming compact spherical loudspeaker arrays were introduced by [PERSON] and [PERSON] [15; 16] for the application in electroacoustic music. We introduced the spherical beamforming technology behind the icosahedral loudspeaker IKO in [17], cf. Figure 1. Commercial soundbars [18] or the IKO [17] emit sound beams whose directions are controlled as spatialization parameters. Spatialization on beamforming systems relies on the availability of a few pronounced reflections, and it is only precise if they can be precisely controlled. [PERSON] et al [19] describe fundamental studies for beamforming loudspeaker systems by comprehensively establishing experimental level thresholds that such systems should provide in isolating distinct reflection paths from the direct path. In this way, every distinct reflection could be used as additional, virtual loudspeaker-localized with the reflection's direction of arrival. These thresholds extend the experimental studies on the precedence effect to a range, in which, instead of attenuated leading sound, the lagging sound is desired to dominate localization. Despite the level thresholds being often only accomplished for a limited set of the available reflection paths, the control of auditory distance succeeds, which, as in [PERSON] [20], is based on controlling the direct-to-diffuse energy ratio. [PERSON] [21] and [PERSON] [22] present experiments that use compact spherical beamformer arrays to vary distance impressions by crossfading between direct and indirect, rather diffuse sound reinforcement. In previous studies [23; 24; 25; 26], we were able to show the basic characteristics of static and dynamic beamforming in various experiments using stationary and transient sounds.