All files have been professionally synthesized in stereo to the greatest of mathematical precision. There are no repeating parts, as found in a lot of so-called noise files today. They are 44.1kHz 16-bit stereo wav files. These contain rest periods of 30 seconds. Logarithmic sine (Up from 30hz) http://www.mediafire.com/?30ommiwwe1j Arithmetic sine (Up from 30hz) http://www.mediafire.com/?zxmwydmiwzj Pink noise: pink.zip White noise: white.zip I'll take requests for certain waveforms or frequencies/sweeps at any time. All in all, it depends on your taste. I recommend downloading the pink noise and logarithmic sine and putting them on a looping playlist.