The effect of early reflection distribution on perceived stage acoustic conditions

It is widely accepted that performing musicians adjust their technique according to the acoustic conditions they hear on stage. It is likely that a musician performing in favourable acoustic conditions will give a higher quality performance. However, preferred conditions for performers are comparatively less well understood than for audience members. This presents a significant challenge when attempting to design a successful auditorium. Stage acoustic conditions are commonly assessed in terms of the overall energy of early reflections, relative to the direct sound, and reverberation time. These parameters relate to two subjective attributes of high importance to performers. However, these parameters are independent of the spatial or temporal distribution of the reflected energy which, in auditorium acoustics, are known to influence the perception of sound. It is proposed that a similar effect is observed for soloist performers and that these aspects of the soundfield will influence the perceived quality of the acoustic conditions. This research aims to observe how the spatial and temporal distribution of early reflections varies for differing stage enclosures and to determine if these factors influence a soloist’s impression of the stage acoustics. A detailed acoustic survey of eight concert hall stages has been undertaken to characterise how the spatio-temporal distribution of early energy varies under different circumstances. This includes musician related aspects such as position on stage and orientation in addition to venue related features, such as the geometry of the stage enclosure. Spatial soundfield measurement and analysis techniques are developed to enable the spatial and temporal characteristics of early reflections to be observed. A set of objective parameters are developed to formally characterise these observations. An interactive listening test allows experienced musicians to compare a series of virtual stage enclosures by playing their instrument. Test subjects rate each hall in terms of preference and in relation to specific subjective attributes. The listening test uses a real-time auralisation system to render the acoustic conditions of a concert hall, in controlled laboratory conditions. This auralisation is based on Spatial Impulse Response Rendering (SIRR) to accurately render stage acoustic conditions over a loudspeaker array. This research proposes new methods of measuring and assessing stage acoustic conditions which will aid in the design of future auditoria. In addition, this research demonstrates the use of more recent spatial audio techniques in stage acoustic laboratory experiments