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Walker, Bruce N.

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    Map-based Priors for Localization
    (Georgia Institute of Technology, 2004-09) Oh, Sang Min ; Tariq, Sarah ; Walker, Bruce N. ; Dellaert, Frank
    Localization from sensor measurements is a fundamental task for navigation. Particle filters are among the most promising candidates to provide a robust and realtime solution to the localization problem. They instantiate the localization problem as a Bayesian filtering problem and approximate the posterior density over location by a weighted sample set. In this paper, we introduce map-based priors for localization, using the semantic information available in maps to bias the motion model toward areas of higher probability. We show that such priors, under a particular assumption , can easily be incorporated in the particle filter by means of a pseudo likelihood. The resulting filter is more reliable and more accurate. We show experimental results on a GPS-based outdoor people tracker that illustrate the approach and highlight its potential.
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    Auditory navigation performance is affected by waypoint capture radius
    (Georgia Institute of Technology, 2004-07) Lindsay, Jeff. ; Walker, Bruce N.
    Non-speech audio navigation systems can be very effective mobility aids for persons with either temporary or permanent vision loss. Sound design has certainly been shown to be important in such devices [e.g. 1]. In this study we consider the added factor of capture radius. The capture radius of an auditory beacon is defined as the range at which the system considers a user to have reached the waypoint where the beacon is located. 108 participants successfully navigated paths through a virtual world using only nonspeech beacon cues. Performance differed across the capture radius conditions. Further, there was a speed-accuracy tradeoff, which complicates the design decision process. Implications of these results for the design of auditory navigation aids are discussed, as are other ongoing and future studies.
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    Individual differences, cognitive abilities, and the interpretation of auditory graphs
    (Georgia Institute of Technology, 2004-07) Walker, Bruce N. ; Mauney, Lisa M.
    Auditory graphs exploit pattern recognition in the auditory system, but questions remain about the relationship between cognitive abilities, demographics, and sonification interpretation. Subjects completed a magnitude estimation task relating sound dimensions to data dimensions. Subjects also completed a working memory task (2-back task) and a spatial reasoning task (Raven's Progressive Matrices) to assess cognitive abilities. Demographics, such as gender, age, handedness, and musical experience, were also reported and included in the analysis. A stepwise multiple regression analysis was performed to determine the relationship between the independent (cognitive abilities and demographics) and dependent (individual slopes and R-squared values) variables. The regression analysis indicates some support for most of the predictor variables, especially predicting R-squared values. The 2-back task does not seem to contribute significantly to the interpretation of sonifications and auditory graphs. However, Raven's and many of the demographic variables do show predictive value for interpretation of auditory graphs.
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    The audio abacus: Representing a wide range of values with accuracy and precision
    (Georgia Institute of Technology, 2004-07) Godfrey, Justin ; Lindsay, Jeffrey ; Walker, Bruce N.
    Point estimation is a relatively unexplored facet of sonfication. We present a new computer application, the Audio Abacus, designed to transform numbers into tones following the analogy of an abacus. As this is an entirely novel approach to sonifying exact data values, we have begun a systematic line of investigation into the application settings that work most effectively. Results are presented for an initial study. Users were able to perform relatively well with very little practice or training, boding well for this type of display. Further investigations are planned.
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    Creating functional and livable soundscapes for peripheral monitoring of dynamic data
    (Georgia Institute of Technology, 2004-07) Mauney, Bradley S. ; Walker, Bruce N.
    Sonifications must be studied in order to match listener expectancies about data representation in the form of sound. In this study, a system was designed and implemented for dynamically rendering sonifications of simulated real-time data from the stock market. The system read and parsed the stock data then operated unit generators and mixers through a predefined sound mapping to create a `soundscape' of complementary ecological sounds. The sound mapping consisted of a threshold-based model in which a percentage change in price value was mapped to an ecological sound to be played whenever that threshold or gradient had been reached. The system also provided a generic mechanism for fading and transitioning between gradients. The prototype system was presented to stock trader test subjects in their work-listening environment for evaluation as a stand-alone system and in comparison to their preferred tools.