This process of survey and measurement, modelling, analysis and auralisation helps to provide an additional insight as to the properties and experience of being within a given space or environment, and can also be used to measure and map related changes over a period of time. As this research has developed, a significant body of acoustic data has been generated resulting in the OpenAIR library. This resource has therefore become a record of the acoustics of sites of historic interest around the UK and since expanded to cover additional similar sites around the world, together with outdoor environments and model-based auralisations. As a consequence of the breadth of these data, OpenAIR has also become a key resource for electronic musicians, sound designers, software developers and computer-game authoring houses. When this work was started in 2004 it was informed by the audio technology and computer music resources of the time. In 2004 the technology available to realise and render the acoustic measurements that were to be obtained from the spaces studied was not so common. Real-time multi-channel auralisation required high-performance, high-cost hardware, often confined to research labs, industry and high-end music studios. Software versions of the same, in the form of audio plugins for common desktop computer digital audio workstations, were starting to become more commonplace, and surround-sound recording and audio mixing was also becoming more popular. In 2016 the situation is very different – multi-channel impulse response convolution-based reverberation effects are readily available in most common creative music software applications, and dedicated hardware devices are long since obsolete. It is now even possible to render an auralisation using a standard web browser on a mobile device. OpenAIR is one of many online resources for exploring the reverberation and acoustics of real and modelled spaces through the availability of impulse responses. What sets OpenAIR apart is the open-source data made available through a Creative Commons Licence, and that it supports multiple, uncompressed, high-resolution audio formats. The aim of this ongoing project is to survey, preserve, re-create and creatively apply the acoustic properties of the heritage spaces considered. To date, these range considerably across period (Maes Howe, Orkney, dating from 2700 BCE, to the R1 Nuclear Reactor Hall in Stockholm, dating from 1970), size (from the few cubic metres of the Pozzelle di Pirro Zollino underground water system tanks to York Minster's approximate volume of 200,000m³), reverberation time (0.4s at 1kHz for Troller's Gill Iimestone gorge in the Yorkshire Dales to 10s at 1kHz for the Terry's Chocolate Factory warehouse), and geography (Spokane Women's Club, Spokane, USA, to Koli National Forest Park, Finland).
OpenAIR has therefore become a central repository for our research in virtual acoustics and auralisation. It documents and disseminates high quality, spatially encoded impulse responses from buildings and landscapes around the world, as well as simulations from 3D computer models, and anechoic recordings suitable for preparing auralisations of these surveyed sites. In the fields of computer music, sound design and composition, the database has been incorporated under a Creative Commons Licence into leading digital audio workstations: Propellerheads Reason, Presonus Studio One and Ableton Live. These software applications are used in many aspects of modern music and audio production, enabling music composition, audio recording and manipulation, and performers to incorporate electronic music into their live work. A core component of any such software is the ability to apply reverberation modelling to source sounds, and this is now commonly implemented using convolution processing based on measured or modelled impulse responses sets. Hence music producers using such software are beginning to – perhaps unwittingly - explore the acoustics of the past through their appropriation of OpenAIR data. This research has also been used to deliver spatial impulse responses obtained from car cabins and audio assets for computer game sound design, and in 2014 the OpenAIR team were credited in the release of Codemasters' Grid AutoSport, in which this measurement work is featured.
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