This strange face is a spectrogram, a plot of nine seconds of frequency (vertical axis) against time (horizontal axis) of Aphex Twin’s song Equation. Spectrograms are usually used for analysis of sound, and require a lossy domain shift. (Sound is the result of small pressure changes on your ear drums over time; the two elements that define it therefore are pressure/energy and time.) This is the first time I have heard of a case where the sound is derived from the spectrogram.
Edit: changed the order of two words that implied spectrograms can be made from a recording without a domain shift, which I do not think is true. 13-4-2006.