UC Santa Barbara

When a sound source is spatialized over loudspeakers, the source undergoes a series of transformations before it ultimately reaches the listener. The source is first transformed by panning and other spatialization algorithms based on its spatial parameters in what this dissertation calls the virtual field. Next, the source is projected by the loudspeaker array into the acoustic field further transforming the source. The virtual field, loudspeaker array, and acoustic field form the spatial audio field (SAF) which significantly influences how a spatial composition is perceived. This dissertation presents the theory of spatial audio fields and culmination of research and development of new compositional techniques based on manipulation of loudspeaker gain curves in the virtual field. The majority of current spatial techniques focus on manipulation of a source's spatial parameters and parameters of the spatial image. While sources in spatial audio compositions are assigned positions and trajectories that often change throughout the work, the spatialization algorithms of the virtual field are usually fixed, the loudspeaker array does not change, and the acoustic field rarely changes during the performance. Thus the specific SAF used in a given work, whether constructed deliberately as part of the compositional process or constructed arbitrarily, is usually static. The SAF is largely unexplored for new compositional techniques on short musical timescales. As the loudspeakers and acoustic field are physical components of the SAF, changes to each are only practical on larger timescales from musical phrases to form. However, as the virtual field is usually constructed digitally, it can be changed on timescales down to the sample rate. Therefore, the focus of this research is on developing compositional techniques in the virtual field. To carry out this research, an experimental software program was developed that not only allows for realtime spatialization of multiple audio sources, but also allows for realtime changes to the virtual field. This research has led to the development of new compositional elements, methods of synthesis, and spatial extensions to traditional compositional techniques. These methods and techniques are not limited to spatial audio using loudspeakers in a space, but can also be used in spatial audio over headphones where the acoustic field is almost entirely simulated. This opens up possibilities for developing new compositional techniques based on changes to the simulated acoustic field on shorter musical timescales in conjunction with the techniques in the virtual field developed in this research.