Sonified Distance in Sensory Substitution Does Not Always Improve Localization: Comparison With a 2-D and 3-D Handheld Device

Early visual to auditory substitution devices encode 2-D monocular images into sounds while more recent devices use distance information from 3-D sensors. This study assesses whether the addition of sound-encoded distance in recent systems helps to convey the “where” information. This is important to the design of new sensory substitution devices. We conducted experiments for object localization and navigation tasks with a handheld visual to audio substitution system. It comprises 2-D and 3-D modes. Both encode in real-time the position of objects in images captured by a camera. The 3-D mode encodes in addition the distance between the system and the object. Experiments have been conducted with 16 blindfolded sighted participants. For the localization, participants were quicker to understand the scene with the 3-D mode that encodes distances. On the other hand, with the 2-D only mode, they were able to compensate for the lack of distance encoding after a small training. For the navigation, participants were as good with the 2-D only mode than with the 3-D mode encoding distance.