No abstract

A new representation of audio noise signals is proposed, based on symmetric -stable (S S) distributions in order to better model the outliers that exist in real signals. This representation addresses a shortcoming of the Gaussian model, namely, the fact that it is not well suited for describing signals with impulsive behavior. The -stable and Gaussian methods are used to model measured noise signals. It is demonstrated that the -stable distribution, which has heavier tails than the Gaussian distribution, gives a much better approximation to real-world audio signals. The significance of these results is shown by considering the time delay estimation (TDE) problem for source localization in teleimmersion applications. In order to achieve robust sound source localization, a novel time delay estimation approach is proposed. It is based on fractional lower order statistics (FLOS), which mitigate the effects of heavy-tailed noise. An improvement in TDE performance is demonstrated using FLOS that is up to a factor of four better than what can be achieved with second-order statistics.Index Terms-Microphone arrays, symmetric alpha-stable distributions, time delay estimation, wideband array signal processing.

Numerous applications are currently envisioned for immersive audio systems. The principal function of such systems is to synthesize, manipulate, and render sound fields in real time. In this paper, we examine several fundamental and technological limitations that impede the development of seamless immersive audio systems. Such limitations stem from signal-processing requirements, acoustical considerations, human listening characteristics, and listener movement. We present a brief historical overview to outline the development of immersive audio technologies and discuss the performance and future research directions of immersive audio systems with respect to such limits. Last, we present a novel desktop audio system with integrated listener-tracking capability that circumvents several of the technological limitations faced by today's digital audio workstations.

We present the architecture, technology and experimental applications of a real-time, multi-site, interactive and collaborative environment called Distributed Immersive Performance (DIP). The objective of DIP is to develop the technology for live, interactive musical performances in which the participants -subsets of musicians, the conductor and the audience -are in different physical locations and are interconnected by very high fidelity multichannel audio and video links. DIP is a specific realization of broader immersive technology -the creation of the complete aural and visual ambience that places a person or a group of people in a virtual space where they can experience events occurring at a remote site or communicate naturally regardless of their location. The DIP experimental system has interaction sites and servers in different locations on the USC campus and at several partners, including the New World Symphony of Miami Beach, FL. The sites have different types of equipment to test the effects of video and audio fidelity on the ease of use and functionality for different applications. Many sites have high-definition (HD) video or digital video (DV) quality images projected onto wide screen wall displays completely integrated with an immersive audio reproduction system for a seamless, fully three-dimensional aural environment with the correct spatial sound localization for participants. The system is capable of storage and playback of the many streams of synchronized audio and video data (immersidata), and utilizes novel protocols for the low-latency, seamless, synchronized realtime delivery of immersidata over local area networks and widearea networks such as Internet2. We discuss several recent interactive experiments using the system and many technical challenges common to the DIP scenario and a broader range of applications.These challenges include: (1). low latency continuous media (CM) stream transmission, synchronization and data loss management; (2). low latency, real-time video and multichannel immersive audio acquisition and rendering; (3). realtime continuous media stream recording, storage, playback; (4). human factors studies: psychophysical, perceptual, artistic, performance evaluation; (5). robust integration of all these technical areas into a seamless presentation to the participants.