The aesthetics of the Bayreuth Festspielhaus explained by means of acoustic measurements and simulations

The Bayreuth Festspielhaus (BF) is unique; the theatre was conceived by Richard Wagner to host the complex of Ring and it was opened in 1876. After this date, the BF played a key role in the development of the modern opera house and no other opera house is so discussed among non acousticians for its acoustics. Some solutions applied for the first time in this theatre influenced later opera houses: the position of all seats within the line of sight of the stage, the dimming of the lights during representations, the double proscenium arch and -- the most relevant one -- the use of a deep orchestra pit (mystic gulf). However, in spite of the worldwide fame of the BF, the values assumed by the main room acoustics criteria in this hall have been reported and analysed in few works. The aim of the present work is to analyse the key role played by BF in the history of the opera basing on acoustic measurements and then propose tools for an immersive virtual experience of this space. All the main acoustic room criteria have been extracted and commented taking into account the peculiarity of the Wagnerian opera. Measured criteria have been related to the subjective impressions reported in the non technical literature. Furthermore, a numerical model of the theatre has been created. The model was calibrated by using the measured room criteria, following state-of-the-art techniques. A whole orchestra (105 musicians) plus singers (3 singers and a choir of 10 persons) was simulated on a computer. The present and the original acoustics of the hall were recreated by rendering binaural room impulse responses (BRIRs) for three listener positions in the audience. These tools allow to experience the Wagner's idea of a ``new opera'' from a perceptual point of view. The CAD model and the simulated BRIRs of the BF are freely available for academic uses.