Simulación y propuesta de un sistema de sonorización espacial para el Teatro Buero Vallejo

Abstract

In this project a tridimensional audio playback system is proposed for the auditorium of the Teatro Buero Vallejo, located in Guadalajara, using the Ambisonics spatial sonorization technology based on scenes, which is the most widely used nowadays. For that purpose, at the beginning of this document, an investigation into some of the traditional spatial sonorization technologies is made. Subsequently, this project performs a deep research about Ambisonics, covering from its operating principle and possible formats, to its codification and decodification processes. It also studies the most common sound field capture techniques, as well as some signal processing for manipulating the spatial content and the pros and cons of this technology over other traditional sound systems. The motivation of implementing this technology is its ability for recreating any real or simulated sound field around the listener, offering the possibility to perform real time signal processing for a manipulation of the spatial content, with a low computational cost. This technology also allows a non-strict speaker distribution, which is an advantage that facilitate dealing with geometrical limitations when designing the speaker placement in rooms with irregular forms. In summary, Ambisonics offers an immersive experience that may be interesting for some kinds of events in the auditorium, such as theatrical works or shows with live music that may find useful introducing tridimensional audio effects in their performances. For evaluating the proposed speaker system, it is necessary to perform computational simulations before installing it. For that purpose, in this project a tridimensional model of the auditorium is built using the software EASE (Enhanced Acoustic Simulator for Engineers) from the AFMG company. Firstly, the auditorium’s geometry is built for the model, and then the materials are assigned to its faces. Since this model contains approximations due to the complexity of the actual geometry of the theater and the uncertainty of the acoustic properties of the materials, it is required to calibrate it: after taking measurements in situ that enable us to characterize the acoustic of the auditorium, the absorption and scattering coefficients of the assigned materials are adjusted until the simulations performed in EASE and the taken measurements are similar. Once the error is considered small enough, it is deemed that the model is finished and serves as a valid replica of the actual auditorium, so the sonorization system can be evaluated on it. Taking into account the dimensions of the auditorium and the previous investigation into Ambisonics technology, this project proposes an adapted audio system for third order ambisonic signals, with a speaker distribution suitable for the room. Since a decodification of the ambisonic signals is also needed for its playback through the system, this project also offers an Ambisonics decoder programmed on Matlab. This decoder is scalable in order (up to three) and number of speakers, as well as in the speaker and sweet spot positions. This enables the possibility of implementing, with this same decoder, alternative speaker distributions that the one proposed in this project, as well as designing other Ambisonic systems in different situations aside the chosen auditorium for this project. Once the sonorization system, the test signals and the decodification are finished, a set of auralizations are made in EASE. Playing these audio files through headphones enables us to perceive what a listener at a certain point of the theater would approximately hear if the decoded signal test were played through the speakers. In this way, it is possible to evaluate the proposed sonorization system in approximate terms. Finally, this project evaluates the sonorization and clarity estimated for the proposed system. At the end of the document, the regulatory framework, the estimated budget and the social and economic impact of this project on the theater and the city are exposed.