Robust Time Difference Estimation for Unknown Microphone Positions with Reverberation

In this thesis a system is developed for robust time difference estimation for multiple microphones in reverberant environments, without any knowledge of the 3D positions of the microphones or the room. RANSAC is used to find line segments in sets of frames containing a number of the largest GCC-PHAT peaks. Focus is on real experiments with one moving sound source continuously playing music. The estimated time differences can be used to find the microphone positions, track the sound source, and estimate flat surfaces in the room. The system has been evaluated on real data with manually annotated ground truth in order to estimate the precision of the system in terms of true positives and false positives. The algorithms have also been incorporated into a system that takes a number of sound files as input and produces the microphone positions, sound path motion and reverberant structures. The complete system has been evaluated on real data with promising results

Source Localization in Reverberant Environments by Consistent Peak Selection

Acoustic source localization in the presence of reverberation is a difficult task. Conventional approaches, based on time delay estimation performed by generalized cross correlation (GCC) on a set of microphone pairs, followed by geometric triangulation, are often unsatisfactory. Prefiltering is usually adopted to reduce the spurious peaks due to reflections. In this work an alternative strategy is proposed, based on the concept that secondary peaks of the GCCs can be crucial in order to correctly locate the source. More specifically, an iterative weighting procedure is introduced, based on the rationale that peaks corresponding to the actual source position should be consistently weighted. The position estimate is then refined by use of an effective and fast clustering technique. Experimental results on simulated data demonstrate the effectiveness of the proposed solution. © 2007 IEEE

A Framework for Site-Specific Spatial Audio Applications

As audio recording and reproduction technology has advanced over the past five decades, increasing attention has been paid to recreating the highly spatialised listening experience we understand from our physical environment. This is the logical next step in the quest for increasing audio clarity, particularly as virtual reality gaming and augmented reality experiences become more widespread. This study sought to develop and demonstrate a technical framework for the production of site-specific audio-based works that is user-friendly and cost effective. The system was intended to be used by existing content producers and audio programmers to work collaboratively with a range of site-based organisations such as museums and galleries to produce an audio augmentation of the physicality of the space. This research was guided by four key aims: 1. Demonstrate a compositional method for immersive spatial audio that references the novel physical environment and the listener’s movement within it. 2. Describe a framework for the development and deployment of a spatial audio visitor technology system. 3. Prototype a naturalistic method for the delivery and navigation of contextual information via audio. 4. Deploy, demonstrate, and evaluate a spatial audio experience within a representative environment. The resulting system makes use of a range of existing technologies to provide a development experience and output that meets a clearly defined set of criteria. Furthermore, a case study application has been developed that demonstrates the use of the system to augment a selection of six paintings in a gallery space. For each of these paintings, a creative spatial composition was produced that demonstrates the principles of spatial composition discussed in this thesis. A spoken informational layer sits on top of this acting as a museum audio guide, featuring navigation using head gestures for a hands-free experience. This thesis presents a detailed discussion of the artistic intentions and techniques employed in the production of the six soundscapes, as well as an evaluation of the resulting application in use in a public gallery space