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The acoustic and auditory properties of individual musical instruments have been extensively studied over recent decades, however, their sonic interplay within a musical ensemble remains under-explored. Given their considerable importance across various fields, aspects of ensemble sound, such as blending of instruments, perceptual relevance of directivity of instruments, and the role of room acoustics, demand comprehensive evaluations and an interdisciplinary approach. This study aims to improve the perceptually motivated acoustic representation of instruments in joint performance in both real and virtual acoustic domains, by exploring different stages of these aspects in musically realistic contexts.
An explorative listening test with live string ensemble performance suggested that the characteristics of the acoustic environment considerably influence the blending of violins playing in unison. Combining methods of Machine Learning and Music Information Retrieval, a computational modelling approach is proposed to classify sound samples from an ensemble recording according to perceived blending. Proving this classification to be effective for monophonically rendered sound samples of two violins from in-situ environments, without requiring the individual source recordings marks a first step towards comprehensive blending modelling. Furthermore, the applicability of close-microphone recordings for auralization of a perceptually convincing ensemble sound was successfully demonstrated.
Advancing previous research in directivity perception, it could be demonstrated that the room acoustics have a greater impact on the orientation perception of sources than their directivity. By involving instruments with distinct radiation directivities in a variety of acoustic environments, the major acoustical parameters influencing the orientation perception have been explored. Examining musical instruments with their inherent dynamic directivity against loudspeakers in in-situ conditions showed that their distinction becomes obscured under specific acoustic conditions. These findings led to a pilot study on the perceptual relevance of high-order directivity modelling of individual sources forming an ensemble. Results indicate, that even with an increasing number of sources, their detailed directivity characteristics remain pivotal for auralizing ensemble performance.
The role of room acoustics in shaping the overall blending is shown to be dependent on the source-level blending. A computational model for predicting overall perceived blending in musical performance using source-level blending ratings and room acoustical parameters was suggested and validated. Analysis of its feature importance revealed that the room acoustic contribution to the overall blending impression is nearly as significant as the blending between instruments at the source level. By emphasizing and detailing relations between musical blending, directivity perception, and auralization aspects, this thesis contributes to the advancement of ensemble sound research and offers insights pertinent to music performance and perception research, virtual acoustics, and related fields.
Room acoustic conditions are an inherent element of every live music performance. They interact with the sound that is generated by the musicians, modifying the characteristics of the sound received by audience and musicians. While listeners usually play a passive role in the context of a live performance, musicians are part of a feedback loop composed by themselves, their instruments, and the room. The goal of this thesis is to characterize the effects of room acoustics in live performances, by studying the acoustical preferences of musicians and characterizing potential performance adjustments implemented by solo players while adapting their interpretation to the room acoustic conditions.
To conduct systematic experiments, a virtual acoustic environment that replicates acoustic conditions of real rooms in laboratory conditions is implemented. Room impulse responses of performance rooms are measured and parametrized using spatial measurement techniques. The responses are later resynthesized and convolved in real-time with the sound generated by a musician. The resulting sound is reproduced through a 3D loudspeaker set-up, allowing musicians to perform under replicated acoustic conditions of measured rooms in real-time. The system is used to conduct pilot studies on stage acoustics preferences of semi-professional trumpet players, and to study the impact of room acoustics on potential performance adjustments of live performance. To this end, musical pieces are recorded under different acoustic conditions and later analyzed. A second experiment is performed with organ players in the Detmold Konzerthaus. The reverberation time of the hall is modified using a reverberation enhancement system, and live performances are recorded under different acoustic conditions using a MIDI interface. Similarly to the trumpet players, the recordings are analyzed to evaluate the extent of the performance adjustments. Finally, listening tests are conducted to assess the perceived impact of those adjustments by listeners.
Results of the experiments suggest that musicians systematically adjust their performance to accommodate room acoustic conditions and listeners are generally able to perceive these changes. Trumpet players tend to decrease the sound level and sound brightness when exposed to longer and stronger reverberation. Some players adjust as well musical dynamics and aspects related to the tempo of their performance, although generalized trends are not observed. Dry environments are usually preferred to practice instrument technique, while longer reverberation times are preferred in concert conditions. Additionally, the presence of a sufficient amount of early energy contributes positively to the musicians’ comfort, regardless of the direction of incidence of this sound energy. Organ players are prone to modifying the temporal aspects of the performance, generally decreasing the overall tempo and increasing the length of breaks in more reverberant environments. The musical character of the played excerpts seems to play an important role, and while for some pieces changes are generalized and systematic, the performance of other pieces with soft dynamics and little contrast is generally less affected by room acoustics.