The brain fills in what it expects in your peripheral vision. For example, you can see colors in your peripheral vision, but it is only an illusion made in the brain.
You can see in your peripheral vision, but not clearly, and not colors. This is because the cones in the eye are all in the center, and they are responsible for most of your daytime vision. Around the cones are rods, they are used for night vision and motion detection.
The colors you see in your peripheral vision are not real, but an illusion made by the brain.
I know, it's less clear, but there are colors, I have tested that with a random color generator. The colors are imprecise in the far periphery, but the basic colors can still be seen.
I guess my vision may indeed be abnormal as somebody else above suggested, since I don't get the blid spot in the central vision in the dark, either.
As for the sound, I think you just learn to hear the sine waves as speech - I tried to convert a part of audiobook (that I haven't listened to before) and I can understand it a little bit.
I used praat with this script (it doesn't seem to like long sounds): http://www.mrc-cbu.cam.ac.uk/people/matt.davis/sine-wave-spe...
