  Tens of millions of people live blind, and their number is ever increasing.
Visual-to-auditory sensory substitution (SS) encompasses a family of cheap,
generic solutions to assist the visually impaired by conveying visual
information through sound. The required SS training is lengthy: months of
effort is necessary to reach a practical level of adaptation. There are two
reasons for the tedious training process: the elongated substituting audio
signal, and the disregard for the compressive characteristics of the human
hearing system. To overcome these obstacles, we developed a novel class of SS
methods, by training deep recurrent autoencoders for image-to-sound conversion.
We successfully trained deep learning models on different datasets to execute
visual-to-auditory stimulus conversion. By constraining the visual space, we
demonstrated the viability of shortened substituting audio signals, while
proposing mechanisms, such as the integration of computational hearing models,
to optimally convey visual features in the substituting stimulus as
perceptually discernible auditory components. We tested our approach in two
separate cases. In the first experiment, the author went blindfolded for 5
days, while performing SS training on hand posture discrimination. The second
experiment assessed the accuracy of reaching movements towards objects on a
table. In both test cases, above-chance-level accuracy was attained after a few
hours of training. Our novel SS architecture broadens the horizon of
rehabilitation methods engineered for the visually impaired. Further
improvements on the proposed model shall yield hastened rehabilitation of the
blind and a wider adaptation of SS devices as a consequence.
