2. Auditory Navigation with an Application in Building Emergency Evacuation Peter Rutherford and Deborah Withington University of Leeds, School of Biomedical Sciences

3. Audition at a Warning Level The ability of humans to determine the location of sound in three dimensional space has been an essential tool for our survival.

4. Audition at a Warning Level Some of the earliest research into virtual acoustics looked at guiding the eyes to targets in cluttered visual displays. From an electrophysiological perspective, when light and sound are presented from a spatially coincident location, localization performance increases by up to 468%.

5. Audition at a Warning Level - Auditory Navigation You are trapped in an unfamiliar, smoke filled building. Surrounding you is dense, black, noxious smoke. How do you get out? Easy, by using a navigation beacon, you can follow your ears! However, how do we test such a system on people? We cannot expose them to the dangers of a burning building.

6. Audition at a Warning Level - Auditory Navigation Problems:  Localization is highly dependent upon the type of sound stimuli presented.  Localization is also affected by the environment in which sound propagates.  Static modelling is limited for localization experiments.  Dynamic modelling is desirable but is computationally expensive and difficult to do.

7. DataofEnvironment SoundFieldModelling DistributionofVirtual Sound Sources BinauralSimulation BinauralImpulseResponse Convolution AnechoicSignal people talking navigation beacon fire alarm footsteps left ear right ear The Simulation Cycle

8. How Does it Work in a VR Setup? Visual Model Acoustic Model GraphicsRendering AcousticRendering TCP/IP Locational Information for Source and Receiver Raw Anechoic Sound File from Graphics Engine Loudspeaker Presentation Headphone Presentation ConvolvedAudioStream

9. What Are We Going to Do With It?  Model a series of virtual environments, including shopping malls, atria, long corridors, ship and aircraft interiors.  Insert our navigation beacons.  Look at how they work on people with various degrees of visual and hearing impairment.  See how we can improve on earlier research, and discover the exact limitations of static acoustics research.

10. What Problems Have We Faced?  Latency and Synchronisation – If there is a sufficient temporal lag between the visual and acoustic hardware, task performance and presence are affected.  Detailed room impulse calculations are still computationally expensive. For our work, these are done offline. We are only simulating direct sound and early reflections which reduce time with reverberation added in statistically.  Accuracy of Computer Models - We have measured real rooms and validate them against our simulations. Results are acceptable.  Generalisation of Listener’s Ears – Mathematical transfer functions of individual listener’s ears are proving very difficult to incorporate into the model.

11. How Far on are We?  Integration of visual and auditory hardware / software completed. This was more difficult than anticipated.  Preliminary ‘mock’ experiments show that concepts work.  These experiments also highlight some interesting acoustic phenomena which are being fed back into the simulation loop.