Holophonic Sources HOLOPHONIC SYNTHESIS OF MUSICAL SOURCES

The composition of a soundfield containing complex nearfield sources has interesting musical applications. A method is presented here using freefield expansions about exterior points of a harmonic multipole field. A derivation and verification are included. Binaural rendering is the natural method for displaying such soundfields. Some possible musical applications are discussed. INTRODUCTION The spatial content of sound is an important part of how it is perceived. This has been reflected in the production of music through the ages, though the spatial acoustics of auditoria and the way sound is projected from musical sources. Through the development of the loudspeaker, and later digital signal processing, the possibilities for generating and controlling spatial sound has increased greatly. The traditions of electroacoustic and acousmatic music have explored these areas, and have sought to explicitly portray spatial qualities as musical attributes, both in recording and live performance. In mainstream recording, there is an increasing interest in spatial sound, as stereo is being superseded with 5.1 systems. Here we are concerned, in particular, with synthesizing complex virtual sources, with dynamic control over the location and orientation of the sources. It should be possible to capture and manipulate the experience of listening to a rich source such as a violin in close proximity, rather than working with the current static methods of recording. Similarly, purely synthetic sources could be created, which have spatial variety associated with traditional instruments. Good results have been achieved for synthesizing distant sources, which reach the listener as plane waves. Distance perception can be simulated using distance filtering and reverberation balance. It is also possible in low-order Ambisonic systems, (Gerzon 1992; Gerzon 1985), to approximately synthesize a diffuse source at varying distance, (Menzies 1999; Menzies 2002), which can be useful in a creative setting. Soundfield synthesis of an object with non-uniform directivity has been considered in the farfield using spherical harmonic representation, (Menzies 1999; Menzies 2002). With the development of high-order acoustic field construction, the simulation of nearfield