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

Lead Research Organisation: University of York
Department Name: Electronics

Abstract

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.

Planned Impact

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.

Publications

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Southern A (2013) Room Impulse Response Synthesis and Validation Using a Hybrid Acoustic Model in IEEE Transactions on Audio, Speech, and Language Processing

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Southern A (2012) Spatial Encoding of Finite Difference Time Domain Acoustic Models for Auralization in IEEE Transactions on Audio, Speech, and Language Processing

 
Description 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. The aim of this visit was 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 resulted in the following objectives: (1) Consolidation of code into an appropriate framework for carrying out this benchmark study. Finite Difference Time Domain (FDTD) wave simulation work was carried out in prototype Matlab code and using the Aalto developed WaveModeller software that integrates with Google Sketchup for 3D Design and includes GPU acceleration based on the NVIDIA CUDA library. Work is ongoing to develop an optimal modular design and simulation strategy suitable for wider distribution and use within the community. (2) design, carry out and write up testing of new room acoustic prediction and auralisation methods; Three papers have been completed and are now all published. The first presents a generic framework for higher order ambisonic encoding of FDTD models based on a circular array of omnidirectional receivers, and is demonstrated to give good objective and subjective results (published). The second paper explores source excitation strategies for FDTD room acoustic modelling. The third paper is the first to offer a more complete testing of a hybrid room acoustics algorithm, based on analytical testing, use of established metrics and real-world simulation scenarios. (3) organise and present results at the first York-Aalto Auralisation Workshop. 19 researchers, including 7 from York, 1 representative from industry, and 11 from Aalto University participated in two days of presentations, exchanges and demonstrations. A summary is available at the given link. This has helped to consolidate our research relationship and will encourage future sharing of results and interactions. Prof. Savioja delivered an invited workshop on using GPUs for audio processing at the 15th International Conference on Digital Audio Effects held in York in September 2012, and has since acted as an external examiner for a PhD in this area at York. The PI spend has also since spent another two periods at Aalto University, with another two research papers in development (one in second round review; the other being revised for resubmission).
Exploitation Route The published outcomes from this project are influencing other relevant work in the area, with citations for the the three journal papers that have emerged to date rising well given their relatively limited time in the public domain. There is also much interest in such approaches in digital games, in terms of effective and efficient acoustic environment modelling, particularly in combination with the much more recent significant developments in VR technology for games. This work is being explored further, in the Digital Creativity Labs Digital Economy Impact Hub project (EP/M023265/1)
Sectors Creative Economy,Digital/Communication/Information Technologies (including Software),Culture, Heritage, Museums and Collections

URL http://www-users.york.ac.uk/~dtm3/Download/YorkAalto_Summary.pdf
 
Description The work on hybrid acoustic modelling explored in this project, was carried out in collaboration with post-doc researcher Dr Alex Southern (amongst others) who was then based within the group at Aalto University. Dr Southern returned to the UK to take up a post at AECOM in their acoustics team, and in collaboration with the PI was able to secure a Royal Society Industry Fellowship Award to be placed on secondment with him at the University of York (Royal Society Industry Fellowship, IF130114). We were able to continue on this work, and have a new journal paper in final stages of completion. It is hoped this work in hybrid modelling will be used as part of Dr Southern's ongoing industry focused research, development and innovation now that he has returned to his role within the company. The ongoing collaboration is also helping to provide mutual support in winning grants and awards, and in securing internship and placement opportunities for University of York students.
First Year Of Impact 2016
Sector Creative Economy,Digital/Communication/Information Technologies (including Software),Culture, Heritage, Museums and Collections
Impact Types Cultural,Economic

 
Description EPSRC Digital Economy Hubs
Amount £4,039,831 (GBP)
Funding ID EP/M023265/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 10/2015 
End 09/2020
 
Description Royal Society Industry Research Fellowships
Amount £72,000 (GBP)
Funding ID IF130114 
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 06/2014 
End 06/2016
 
Description AECOM 
Organisation AECOM Technology Corporation
Department Acoustics
Country United States 
Sector Private 
PI Contribution We have supported a Royal Society Industry Research Fellow from AECOM for a period of 24 months.
Collaborator Contribution The Fellow has contributed knowledge and experience to our wider group and participate in relevant activities of mutual interest, including publications.
Impact One publication (linked via publications list); technology demonstrations.
Start Year 2014
 
Description Aalto University 
Organisation Aalto University
Country Finland 
Sector Academic/University 
PI Contribution We have worked on a number of joint publications and continue to do so.
Collaborator Contribution Aalto University have hosted Damian Murphy and members of his team for short periods at a time up to three months in duration.
Impact We have so far published 3 journal publications, another two are in stages of development and there are a number of relevant conference publications.
Start Year 2007
 
Description Ongoing collaboration with Arup Acoustics Glasgow, based in the area of interactive auralization. 
Organisation Arup Group
Department Acoustic Consulting
Country United Kingdom 
Sector Private 
PI Contribution We organised and managed the I-Hear-Too AHRC funded research network
Collaborator Contribution Members contributed to this network and hosted and event.
Impact A number of events, and follow on funding applications have been developed as part of and beyond the I-Hear-Too project on which this collaboration was founded. A co-supervised PhD with the Arup Glasgow office is still underway.
Start Year 2008