People who have been blind since a young age can sometimes learn to develop a sort of low-grade echolocation. This technique, used by the likes of Ray Charles, Stevie Wonder, Ronnie Milsap, and Ben Underwood, works much the same way as it does in bats and dolphins. But people who have just recently lost their sight can't harness this ability innately. They need the vOICe to do it for them.
Invented by Dr. Peter B.L. Meijer, Principal Scientist at the Netherland's Hemics BV in 1982, the vOICe (as in "Oh, I See") is what's known as a sensory substitution device (SSDs). SSDs instigate a mechanical synthesia—transforming visual information into audible representations—in order to overcome a lost sensory ability. The image below is that of Dr. Meijer mid-conversion.
The vOICe consists of a glasses-mounted camera for collecting visual data, a backpack-carried laptop running the conversion software, and headphones to project the converted sound into the patient's ears, scanning left to right like a sonar sweep. While Meijer did come up with the idea in the early '80s it wasn't until nearly two decades later in 1998 that the necessary components had shrunk to portable sizes and even that used a desktop webcam—which was quickly replaced with a pair of those "spy" sunglasses you find in Skymall. The system still uses spy glasses, though users can also download the software to their smartphone and use its camera instead.
As the vOICe website explains:
The vOICe converts images captured by a camera into "soundscapes" delivered to the user through headphones at a default rate of one soundscape per second. Each soundscape is a left to right scan of the visual scene with frequency representing the image's vertical axis and loudness representing brightness... The user therefore experiences a series of "snapshots" passing from the left to the right ear.
Some studies have suggested that the brain adapts to the long-term use of these devices, rewiring itself to "see" sounds, like Daredevil. Claire Cheskin, a long-time user of the vOICe, told New Scientist that she can interpret full images roughly akin to her lost sight just by listening. "I've sailed across the English Channel and across the North Sea, sometimes using the vOICe to spot landmarks," she said. "The lights on the land were faint but the vOICe could pick them up." What's more, some skilled users able to do the same without the aid of the SSD. The next step will, obviously, be Geordi LaForge-style visors. [PopSci - SeeingWithSound 1, 2, 3 - Images: Seeing With Sound, diagram (below): New Scientist]