ApplPi is a stochastic noise machine that creates a soothing background noise for those who can't work in complete silence or need to mask distracting noise. It creates sound similar to any noise machine, but it's more musical and harmonic. Additionally, you can control the frequency (note) of the sound and choose from built-in presets of noise/sound.
Little java jar to produce brown noise. It sounds much like the engines heard from inside of a well insulated airplane. Four controls: slower, start, faster, & a number field for the Hz of the noise. The default is 440; I preferred 200. It's such a laser-focused app, there's little to foul up. The only dissonant element is the obsolete link in the title bar. That points to the abandoned github page rather than this sourcefourge page. The window is a bit wider than it needs to be as well. But, those are irrelevant to the app, which will be minimized or covered by whatever you're doing, anyway. As an ambiance machine, this is just right. No need to waste electricity on a running fan.