Chroma Doze (white noise) – 3.5

Now you can sleep soundly with the soothing algorithms of Fourier analysis. Just sketch your favorite spectrum, and listen to a generated stream of white/colored noise. If sleep's not your thing, you can also use it with headphones to drown out neighbors, or tweak the settings to erode eardrums and frighten small children. Notable features: No ads or weird permissions.