Free. Plays white noise, and others, perhaps to drown out the neighbors' garbage music playing at midnight or whatever you may need it for. I'm not currently maintaining a Linux version any longer however the Windows version works perfectly in Wine. Using the rate dial may completely reverse desirability/undesirability for certain sounds to some individuals, so feel free to experiment with it. The 46Hz generator creates a pleasant rumble when used with a decent subwoofer that, in my case, completely silences all sounds from adjacent apartments with the speaker in a corner of the room, and cannot be heard at all when I'm not near a wall. Without a subwoofer it will likely have no effect and you might not even hear it.