Perceptually Driven Interactive Sound Propagation for Virtual Environments

Sound simulation and rendering can significantly augment a user‘s sense of presence in virtual environments. Many techniques for sound propagation have been proposed that predict the behavior of sound as it interacts with the environment and is received by the user. At a broad level, the propagation algorithms can be classified into reverberation filters, geometric methods, and wave-based methods. In practice, heuristic methods based on reverberation filters are simple to implement and have a low computational overhead, while wave-based algorithms are limited to static scenes and involve extensive precomputation. However, relatively little work has been done on the psychoacoustic characterization of different propagation algorithms, and evaluating the relationship between scientific accuracy and perceptual benefits.In this dissertation, we present perceptual evaluations of sound propagation methods and their ability to model complex acoustic effects for virtual environments. Our results indicate that scientifically accurate methods for reverberation and diffraction do result in increased perceptual differentiation. Based on these evaluations, we present two novel hybrid sound propagation methods that combine the accuracy of wave-based methods with the speed of geometric methods for interactive sound propagation in dynamic scenes.Our first algorithm couples modal sound synthesis with geometric sound propagation using wave-based sound radiation to perform mode-aware sound propagation. We introduce diffraction kernels of rigid objects,which encapsulate the sound diffraction behaviors of individual objects in the free space and are then used to simulate plausible diffraction effects using an interactive path tracing algorithm. Finally, we present a novel perceptual driven metric that can be used to accelerate the computation of late reverberation to enable plausible simulation of reverberation with a low runtime overhead. We highlight the benefits of our novel propagation algorithms in different scenarios.Doctor of Philosoph

Acoustical Ranging Techniques in Embedded Wireless Sensor Networked Devices

Location sensing provides endless opportunities for a wide range of applications in GPS-obstructed environments; where, typically, there is a need for higher degree of accuracy. In this article, we focus on robust range estimation, an important prerequisite for fine-grained localization. Motivated by the promise of acoustic in delivering high ranging accuracy, we present the design, implementation and evaluation of acoustic (both ultrasound and audible) ranging systems.We distill the limitations of acoustic ranging; and present efficient signal designs and detection algorithms to overcome the challenges of coverage, range, accuracy/resolution, tolerance to Doppler’s effect, and audible intensity. We evaluate our proposed techniques experimentally on TWEET, a low-power platform purpose-built for acoustic ranging applications. Our experiments demonstrate an operational range of 20 m (outdoor) and an average accuracy 2 cm in the ultrasound domain. Finally, we present the design of an audible-range acoustic tracking service that encompasses the benefits of a near-inaudible acoustic broadband chirp and approximately two times increase in Doppler tolerance to achieve better performance

VR-based Soundscape Evaluation: Auralising the Sound from Audio Rendering, Reflection Modelling to Source Synthesis in the Acoustic Environment

Soundscape has been growing as a research field associated with acoustics, urban planning, environmental psychology and other disciplines since it was first introduced in the 1960s. To assess soundscapes, subjective validation is frequently integrated with soundscape reproduction. However, the existing soundscape standards do not give clear reproduction specifications to recreate a virtual sound environment. Selecting appropriate audio rendering methods, simulating sound propagation, and synthesising non-point sound sources remain major challenges for researchers. This thesis therefore attempts to give alternative or simplified strategies to reproduce a virtual sound environment by suggesting binaural or monaural audio renderings, reflection modelling during sound propagation, and less synthesis points of non-point sources. To solve these unclear issues, a systematic review of original studies first examines the ecological validity of immersive virtual reality in soundscape evaluation. Through recording and reproducing audio-visual stimuli of sound environments, participants give their subjective responses according to the structured questionnaires. Thus, different audio rendering, reflection modelling, and source synthesis methods are validated by subjective evaluation. The results of this thesis reveal that a rational setup of VR techniques and evaluation methods will be a solid foundation for soundscape evaluation with reliable ecological validity. For soundscape audio rendering, the binaural rendering still dominates the soundscape evaluation compared with the monaural. For sound propagation with consideration of different reflection conditions, fewer orders can be employed during sound reflection to assess different kinds of sounds in outdoor sound environments through VR experiences. The VR experience combining both HMDs and Ambisonics will significantly strengthen our immersion at low orders. For non-point source synthesis, especially line sources, when adequate synthesis points reach the threshold of the minimum audible angle, human ears cannot distinguish the location of the synthesised sound sources in the horizontal plane, thus increasing immersion significantly. These minimum specifications and simplifications refine the understanding of soundscape reproduction, and the findings will be beneficial for researchers and engineers in determining appropriate audio rendering, sound propagation modelling, and non-point source synthesis strategies