Preserving the acoustical heritage of historical buildings

The use of virtual reality and auralization techniques has opened new possibilities for the study of acoustical conditions in historic buildings. With reference to some recent and current projects the paper describes the steps in the process and how new technology may be used to overcome some of the difficulties involved. If the building exists as a whole or partly the first step is collection of geometrical and architectural data from the site. The level of detail may be huge, e.g. if laser scanning is used for providing the geometrical data, and some degree of simplification may be necessary for the acoustical model. Measurement of room acoustic parameters may be very useful for comparisons with the computer model, which must then first be made to represent the present state of the building. This allows adjusting the absorption and scattering data in the model to obtain the best possible agreement with the present state building. Next step is to identify what historic conditions that should be reconstructions, especially architectural details, surface materials, obstacles, textiles, performing persons and audience, and typical sounds or music. The computer model is then modified according to these data and sounds recorded in an anechoic environment. Modelling a large number of simultaneous sources, e.g. from a crowd is another challenge. Finally, some applications of the acoustical reconstructions are discussed.