Visual experiences in the blind induced by an auditory sensory substitution device.

In this report, the phenomenology of two blind users of a sensory substitution device - "The vOICe" - that converts visual images to auditory signals is described. The users both report detailed visual phenomenology that developed within months of immersive use and has continued to evolve over a period of years. This visual phenomenology, although triggered through use of The vOICe, is likely to depend not only on online visualization of the auditory signal but also on the users' previous (albeit distant) experience of veridical vision (e.g. knowledge of shapes and visual perspective). Once established, the sensory substitution mapping between the auditory and visual domains is not confined to when the device is worn and, thus, may constitute an example of acquired synaesthesia.