Sound Spatialisation

Towards the end of the nineteenth century two inventions, the telephone and the phonograph, appeared which were to change the way music was dealt with. Prior to the developments they brought about, every musical performance was indivisible from its place in time and space. Their appearance meant that music could be presented remotely in both time and space from its origin. This has inevitably resulted in various forms of distortion nonlinear, spectral, temporal, spatial, of the original. Whilst it has proved relatively easy to deal satisfactorily with the first three so that we can now present “remoted” music which is excellent in all of those three aspects, removing the distortions in the spatial presentation has proved far more intractable. Even the best systems in use today for sound “spatialisation” are relatively crude, allowing for little more than the creation of an illusion, sometimes very good, more often poor. However, despite this, the creative use of sound spatialisation is becoming more and more important, whether for serious avant-garde composers, computer game designers, in cinema, television and multimedia productions or in audio recording. It is anticipated that the demand will escalate even more with the appearance of DVD with its multiple audio channel capability. This tutorial paper briefly covers the basic directional hearing mechanisms of the human brain before examining in more detail the various different ways of dealing with sound spatialisation, starting with headphone related technologies such as binaural and transaural. Loudspeaker-based systems will then be covered, starting with conventional stereo followed by cinema style surround sound systems. Finally a true 3-d system, Ambisonics, will be examined. The advantages and limitations of all the systems, both aurally and in terms of difficulty of implementation or control, will be covered. It is hoped to give a number of demonstrations.