The pavement conditions in snowy regions continuously change as a result of localized snowfall. Individuals with visual impairments unknowingly become disorientated when walking alone. Cognitive maps which are developed during the non-snowy season are not valid during snowy conditions. Braille blocks, landmarks, destination points and street corners are all obscured by snow which make navigation difficult.
We created a guidance system to aid the visually impaired during independent travel in regions with heavy snowfall. This paper studied the effects of sound cues on the navigational turning action of visual impaired persons. Sixteen individuals who are blind were recruited to participate in an investigation of the navigational effects of sound cues. Six loudspeakers, directed towards the ground, were placed at a height of 3m and separated 2-10m from each other, creating an L-shape route (See Figure. 1).
We analyzed the frequency characteristics of background noise at the experiment site and selected three different sound cues for experimental stimuli. The frequency characteristics of our sound cues were different from that of site background noise. Two stationary continuous sound cues (i.e. the sound of a creek (1kHz and 4kHz)), and one intermittent sound cue (i.e. bird's tweets) were used individually or mixed during four different walking conditions. The first walking condition sound cue was 1kHz of the entire creek sound frequency for both X and Y walking axis. Walking condition two was 1kHz and 4kHz of the creek sound frequency for each walking axis, walking condition three combined 1kHz of the creek sound frequency on both X and Y axis with additional birds tweets from two loudspeakers located at the corner. Walking condition four combined all three cues, 1kHz of the creek sound on Y axis, 4kHz of the creek sound on X axis, and the bird tweet from two loudspeakers at the corner.
Our results show that in order to guide the blind persons turning action at a corner, at least two kinds of sound cues are required. Providing two different continuous stationary sound cues on each axis is effective for visually impaired persons to recognize the existence of two crossing axis and assist with turning. However, walking participant feedback suggests that to better distinguish the location of a corner on an L-shape route, another type of sound cue, such as an intermittent sound, might be useful.
