University of Tasmania
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Investigating auditorium acoustics from the perspective of musicians

thesis
posted on 2023-05-27, 23:08 authored by Panton, LF
This thesis investigates auditorium stage acoustics from the perspective of the performing musician, focusing primarily on chamber orchestras playing in a traditional concert setting. Stage acoustics has not been extensively studied in the past, and most studies have focused on full orchestras or small ensembles; however stage acoustics may be of particular importance to the musicians in a chamber orchestra as this is the largest group to perform routinely without a conductor. The aims of the study are to determine which subjective acoustic attributes are important to the chamber musicians and how auditoria could be assessed against these attributes. A broader goal is to inform auditorium and stage design for musicians. The study includes surveying of touring musicians, physical acoustic measurements on stage in auditoria, and modelling of sound propagation through a chamber orchestra with boundary element method (BEM) software. Professional musicians were surveyed during concert tours to control for factors such as repertoire, instrument and position on stage and to minimise the limitations of short acoustical memory. The study encompassed 15 stages, including many of Australia's most important concert halls. High response rates resulted in statistically significant outcomes. Results indicate that the subjective attributes most correlated with overall acoustic impression are ensemble, support, timbre and reverberance. Reverberance was more clearly noted as important when auditoria with inadequate reverberance were included in the surveying set, however adequate reverberance alone was not sufficient for well-liked acoustics. Physical acoustic measurements are often unavoidably made on empty stages, a significant simplification since the orchestra will impact the sound field. To investigate this a BEM model of a chamber orchestra was developed and compared to measurements of a chamber orchestra in situ in a concert hall. The study particularly focused on the degree to which the direct sound and first-order reflections were attenuated and altered by the presence of the orchestra. For the 250 Hz octave band and higher, the empty and occupied stage results differed, particularly for the lateral reflections on stage, whereas the ceiling reflections produced comb filtering but were relatively unaffected by the orchestra. A tilted side wall case showed the orchestra has a reduced effect with a small elevation of the lateral reflections. Musicians' overall acoustic impressions were compared to in situ physical acoustic measurements on the same stages using a 32-channel spherical microphone array, which allowed the directionality of the sound fields to be investigated. It was found that omnidirectional acousticparameters (such as the well-known support measures) have some subjective relevance, which was more clearly observed when auditoria with optimum and non-optimum values were included in the dataset. In purpose-built auditoria with optimum reverberation and support parameters, it was found that the directionality of on-stage sound fields was subjectively important to musicians. A spatial parameter measuring very early sound energy from above relative to the sides and back was explored, and found to correlate at a significant level with musicians subjective ratings, with a preference for more horizontal energy from the sides and back on stage. Overall, this study finds while stage parameters measured with an omnidirectional source and receiver (such as reverberation time and support measures) are useful in identifying musicians subjective preferences another important aspect is the directional distribution of early reflections on stage. The study examines acoustic conditions for musicians with in situ stage measurements and with BEM modelling, and identifies important aspects of stage and auditorium design for chamber orchestra musicians.

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