Using Virtual Reality to Assess the Street Crossing Behavior of Pedestrians With Simulated Macular Degeneration at a Roundabout

This work investigates how pedestrian street crossing behavior at a virtual traffic roundabout is affected by central visual field loss. We exposed participants with normal vision to a first-person virtual experience of central visual field loss of variable size in the form of a simulated scotoma, an area of the visual field with degraded visual acuity. A larger size of scotoma influenced people to select longer gaps between traffic, and to wait longer before initiating a crossing. In addition, a gender difference was found for risk taking behavior. Male subjects tended to take more risk, as indicated by the selection of shorter gaps in traffic and a shorter delay before the initiation of a crossing. Our findings generally replicate those of studies done in real-world conditions using participants afflicted with genuine central vision loss, supporting the hypothesis that virtual reality is a safe and accessible alternative for investigating similar issues of public concern

Discrimination and Estimation of Time-to-Contact for Approaching Traffic Using a Desktop Environment Abstract

Each year, thousands of pedestrians are injured or killed in traffic accidents. Identifying pedestrians ’ perceptual capabilities for street crossing decisions is an important problem. This paper examines this issue by seeking to understand people’s time-to-contact judgments for short-range to long-range times-to-contact in a desktop environment. Two experiments were used to test time-to-contact judgments around 4, 7, and 10 seconds. Both experiments showed subjects videos of a car moving down a road toward the viewer. The first experiment observed subjects ’ ability to discriminate between two different time-to-contact values. The second experiment measured subjects ’ absolute time-to-contact estimates. We found subjects to be accurate at both discriminating and estimating timeto-contact in a desktop environment. However, performance worsens at longer time ranges, those that pedestrians typically use in street-crossing decisions. Our discrimination thresholds are consistent with other time-to-contact work, and thus illustrate that desktop environments are plausible settings to use for time-to-contact studies

Reduced order modeling of head related impulse responses for virtual acoustic displays.

This study investigated the use of reduced order head related impulse response (HRIR) models to improve the computational efficiency in acoustic virtual displays. State space models of varying order were generated from zero-elevation HRIRs using a singular value decomposition technique. A source identification experiment was conducted under anechoic conditions in which three subjects were required to localize sounds in the front horizontal plane. The sounds were either (1) real sources (emitted by individual loudspeakers in a semi-circular array), (2) virtual sources generated from the original HRIRs, or (3) virtual sources generated using reduced order state space models. All virtual sources were created by simultaneous activation of two loudspeakers at ±30° using a virtual source imaging technique based on either the measured or modeled HRIRs. The errors in the perceived direction of the virtual sources generated from the reduced order models were compared to errors in localization using the original HRIRs. The results demonstrate that a very significant reduction in model size can be achieved without significantly affecting the fidelity of the virtual display of horizontally placed sources

The effect of stimulus bandwidth and subject position on horizontal-plane localization with virtual source images

In an anechoic chamber normal-hearing subjects performed a localization task in the frontal horizontal plane. The stimulus was a 200-ms burst of filtered noise. Within a block of trials, half of the presentations (randomly determined) were "real"—presented from single loudspeakers—and the other half were "phantoms"—produced by the simultaneous activation of two loudspeakers at ±30° using a virtual source imaging technique [Takeuchi et al., J. Acoust. Soc. Am. 109, 958–971 (2001)]. Both phantom and real sources spanned the azimuthal range ±80°. When the stimulus was a 4 kHz low-pass filtered noise, rms error was only slighly higher for phantom (D=7.1°) than for real (D=5.5°) sources. For 8 kHz low-pass filtered noise, performance remained about the same for real sources, but increased for phantom sources (D=11.5°). Data will also be reported for conditions in which the subject's position is systematically varied outside the "sweet spot." Results will be discussed in terms of robustness of the virtual imaging technique to stimulus and position factors and its potential usefulness as a tool for the investigation of human auditory spatial perception in static and dynamic environments. [Work supported by NIDCD.