Adaptive Modeling of Details for Physically-based Sound Synthesis and Propagation

In order to create an immersive virtual world, it is crucial to incorporate a realistic aural experience that complements the visual sense. Physically-based sound simulation is a method to achieve this goal and automatically provides audio-visual correspondence. It simulates the physical process of sound: the pressure variations of a medium originated from some vibrating surface (sound synthesis), propagating as waves in space and reaching human ears (sound propagation). The perceived realism of simulated sounds depends on the accuracy of the computation methods and the computational resource available, and oftentimes it is not feasible to use the most accurate technique for all simulation targets. I propose techniques that model the general sense of sounds and their details separately and adaptively to balance the realism and computational costs of sound simulations. For synthesizing liquid sounds, I present a novel approach that generate sounds due to the vibration of resonating bubbles. My approach uses three levels of bubble modeling to control the trade-offs between quality and efficiency: statistical generation from liquid surface configuration,explicitly tracking of spherical bubbles, and decomposition of non-spherical bubbles to spherical harmonics. For synthesizing rigid-body contact sounds, I propose to improve the realism in two levels using example recordings: first, material parameters that preserve the inherent quality of the recorded material are estimated; then extra details from the example recording that are not fully captured by the material parameters are computed and added. For simulating sound propagation in large, complex scenes, I present a novel hybrid approach that couples numerical and geometric acoustic techniques. By decomposing the spatial domain of a scene and applying the more accurate and expensive numerical acoustic techniques only in limited regions, a user is able to allocate computation resources on where it matters most.Doctor of Philosoph

Tracing Analytic Ray Curves for Light and Sound Propagation in Non-Linear Media

The physical world consists of spatially varying media, such as the atmosphere and the ocean, in which light and sound propagates along non-linear trajectories. This presents a challenge to existing ray-tracing based methods, which are widely adopted to simulate propagation due to their efficiency and flexibility, but assume linear rays. We present a novel algorithm that traces analytic ray curves computed from local media gradients, and utilizes the closed-form solutions of both the intersections of the ray curves with planar surfaces, and the travel distance. By constructing an adaptive unstructured mesh, our algorithm is able to model general media profiles that vary in three dimensions with complex boundaries consisting of terrains and other scene objects such as buildings. Our analytic ray curve tracer with the adaptive mesh improves the efficiency considerably over prior methods. We highlight the algorithm's application on simulation of visual and sound propagation in outdoor scenes

Reporting Center Problem for Interval Graphs and Trees

In this thesis we have studied the reporting center problem for interval graphs and trees. The reporting center problem is first introduced in the wireless network field, in which the reporting center strategy is used as one of the strategies for tracking mobile users, and aims at balancing the cost of updating the user position and the cost of locating a mobile user. The reporting center strategy partitions the cellular network into reporting and non-reporting cells. Associated with each reporting cell is a set of non-reporting cells, called its vicinity. Mobile users report their position only when they visit a reporting cell. When a call arrives, the user is searched for only in the vicinity of the last visited reporting center. The size of the vicinity of a reporting center determines the searching and updating cost of the cellular network. It is thus an objective to minimize the number of reporting centers subject to the constraint that the size of the vicinity of each reporting center is bounded by a constant Z>0. The problem has been shown to be NP-hard for arbitrary graphs for Z >= 2. The major contribution of this work is divided into two parts: (1) an algorithm that solves the reporting center problem for arbitrary vicinity for interval graphs, thereby improving a previous result which only solves for vicinity Z=2 for interval graphs and for arbitrary vicinity for proper interval graphs, and (2) an O(n) time algorithm that solves the reporting center problem for trees, which is better than the previous $O(nZ^3)$ result.1 Introduction 1 2 Reporting Center Problem for Interval Graphs 5 2.1 The Staircase Method 5 2.2 Bricks Transformation Method 28 3 Reporting Center Problem for Trees 31 4.Conclusion 53 5.Bibliography 5

Synthesizing contact sounds between textured objects

ABSTRACT We present a new interaction handling model for physics-based sound synthesis in virtual environments. A new three-level surface representation for describing object shapes, visible surface bumpiness, and microscopic roughness (e.g. friction) is proposed to model surface contacts at varying resolutions for automatically simulating rich, complex contact sounds. This new model can capture various types of surface interaction, including sliding, rolling, and impact with a combination of three levels of spatial resolutions. We demonstrate our method by synthesizing complex, varying sounds in several interactive scenarios and a game-like virtual environment. The three-level interaction model for sound synthesis enhances the perceived coherence between audio and visual cues in virtual reality applications