Room Acoustics Prediction and Auralisation: Verification and Testing of New Methods in Room Acoustics Modelling.

Room acoustics simulation - modelling acoustic wave propagation within an enclosed space - is one of the fundamental applications of audio signal processing. Given pre-defined sound-source/listener locations and a surrounding geometry the resulting room impulse response (RIR) of the system can be found. Convolution with this RIR allows any audio signal to be placed in the room at the source location and auditioned by a listener placed at the receiver location. Essentially this allows any sound source to be heard within any room.

There are three main applications for this technology:

(1) Reverberation simulation in music production: all music is composed to be heard in a reverberant environment, whether a concert hall or an algorithm designed to simulate an optimal reverberant field.
(2) Architectural Acoustics: where a building is simulated and auditioned before construction/renovation to determine the resulting acoustic quality and identify any changes that might be appropriate.
(3) Virtual environment modelling: e.g. computer games, virtual reality applications and film/television postproduction, where various sound-sources are placed in and around a virtual environment with the potential for allowing interaction with the space.

Although research at both York and Aalto encompasses standard room acoustics simulation methods based on geometric acoustic techniques (where sound is assumed to behave as a ray of light with the associated limitations involved with making such an assumption) most of our interests and efforts are focused on approaches that solve the acoustic wave equation directly, that therefore offer the potential for a full, complete and accurate simulation of the soundfield within an enclosed space. Recent research has included optimal grid-sampling schemes, frequency dependent diffusing boundaries, spatial encoding for receivers and source excitation strategies. Directional source encoding and real-time auralisation have also been explored, taking the best aspects of wave based and geometric approaches, and offering significant and real potential for both further research and commercial exploitation.
Hence, solutions now exist for the main constituent features of any simulation - source excitation and directivity, wave propagation, boundary interaction, and receiver encoding. This is coupled with new modelling methods and the possibility of using Graphical Processing Units to speed up calculation times. Much of this work to date has been validated using simple, easy to measure objective metrics such as room mode analysis, reverberation time, polar directivity plots, boundary characteristics, etc. It therefore now seems appropriate to tackle more demanding simulations with a view to validating this approach for a broader range of problems. A number of options will be explored including simple, analytically trivial shoebox-shaped rooms, previously published data that formed the basis for a round robin study on room acoustics measurement and simulation, as well as the study of new, complex spaces based on their direct measurement, both physical and acoustic.
The aim of this visit is to facilitate a benchmark study in the use and testing of new room acoustic prediction and auralisation methods for a number of specific ideal and real-world scenarios. This therefore leads to the following objectives: (1) Consolidation of code into an appropriate framework for carrying out this benchmark study; (2) design, carry out and write up testing of new room acoustic prediction and auralisation methods; (3) organise and present results at the first York-Aalto Auralisation Workshop.
The project will result in a consolidation of our research codebase to more easily facilitate both this and future studies, at least one major journal publication and a workshop between York and Aalto to allow initial dissemination and feedback on our results, as well as further encourage the ongoing collaboration between our two groups.

The application of auralisation is focused in the creative industries as part of the digital economy. Collaborators who have already been involved in related projects coordinated by the PI or Professor Savioja come from across the computer game (Sony Computer Entertainment Europe), audio/music production (Sonalksis), acoustic/architectural consultancy (Arup Acoustics) or computer graphics (NVIDIA) industries, and already have a significant presence in this area. The potential for FDTD and FDTD/hybrid simulations as a solution for the broad range of problem areas where accurate room acoustics simulation is needed or desired and highlighted as part of this project, will help to raise the profile of this approach with these and other possible partners and hence result in possible direct routes to potential beneficiaries and associated markets. Existing multidisciplinary collaborations with end users established through previous projects (e.g. computer musicians, sound designers, heritage and museum sectors) provides an important driving influence. There is also a particular opportunity for widening the remit of high quality auralisation beyond the creative industries into healthcare and socio-economic research given the potential for this work in immersive, natural presence telecommunications and the design of the built environment. The impact and benefits for both society, as inhabitants of this built environment, and the individual in terms of relieving isolation and developing new means of social inclusion could be significant.