.flac provides lossless compression, and is one of the four supported audio file types on freesound.org. Audacity, a popular and no-cost audio file editor, can open .flac files. The .flac format may be unfamiliar to audio consumers, but freesound.org is for people who do more with audio than just listen, and for those people .flac should not be a problem.
Congrats I think this would take the prize for black sound as defined somewhat vaguely - "A signal or signal level that is supposed to represent a black area on the object, but has a noise content sufficient to cause the creation of noticeable white spots on the display surface or record medium" at : http://en.wikipedia.org/wiki/Colors_of_noise#Noisy_black
I remember I had an Apple dot matrix printer. I am still very fond of that sound. I printed out a banner for Christmas once and once for my 16th b-day back in 94 and I remember it took half an hour to print out.