Functional Specification of a Distributed and Mobile Architecture for Virtual Sound Space Systems

This paper develops a functional analysis of the augmented reality system presented in [Natkin00]. It also presents the first elements of an experimental architecture and a real example where the system would be used. The system is based on virtual sound reality : spectators are walking into a real space, indoor or outdoor, wearing headphones. They see the real space and at the same time hear a virtual sound space, homeomorphic to the real one. This means that there is a continuous function which maps any trajectory in the real space to a trajectory in the virtual space, thus determining which sound is heard along this trajectory. The synthesis of the virtual sound along a trajectory may depend on many factors : speed of the spectator, past movements of the spectator, current or past position of others spectators, random events and so on. Moreover special rules or constraints will be added, considering the kind of application desired : quality of sound needed, maximum number of spectators using the system at the same time, interactions between spectators (or lack of), complexity of the sound synthesis... Possible fields of application include art installations, personal guided visits through a space, audio help to drivers in a reduced visibility area, audio help in the maintenance of industrial plants.... In this paper we present a functional analysis of the system and a general distributed architecture using both ground and mobile computers. We address in details the localization, transmission and spatialization functions and the time-space-bandwidth complexity of these functions. This leads to a classification of the possible distributed designs according to application constraints. Then we consider an art installation application "The Persian Carpet", proposed by the composer Cecile Le Prado. The specific aesthetic constraints lead to a particular solution of the general design proposed.