From the Battle for Wesnoth team:

Wesnoth is sponsoring a $200 bounty for an environmental sound loop.

We're looking for background audio, explicitly NOT MUSIC, but just recordings of the sound made in a natural environment.  We're asking for this because the available sounds in public-domain libraries, that we can find, are not suitable for our needs - we probably want you to go out and record something new.  We may post a series of these bounties, if this pans out nicely.

Specifically, we're looking for a recording of swamp or marshland that conveys a gloomy, fetid atmosphere.  Not a healthy, normal marshland, in which you'd hear the breeze, the rustling of the wind, and an immense amount of birdsong, but a rotting, "evil" marsh, filled with dying plants, and an overall sense of decay and wrongness.  For a literary/film reference, something like the "dead marshes" in lord of the rings.

Probable components would include the sound of bubbling mud (like in yellowstone-style mud pits), gurgling, the sound of steam, and maybe the sound of clouds of buzzing mites and flies.  It is entirely possible that you won't necessarily have to record a real marsh to get something that sounds like the above, and can just composite stuff together (in fact, it may even be necessary, since the intended effect isn't strictly natural).

We need a loop that is about 3-5 minutes long.  Unlike many other game genres, wesnoth stays fixated on the same environment for a very long stretch of time (30-150 minutes per level), so we need a long loop with enough variety to not wear itself out.  The final clip should be provided in either wav/ogg at 44kbps, with stereo sound, and will be released under the public-domain (CC0) license.

We reserve the right to approve or reject the work based on our own discretion.

If you have any questions (or a submission for review), please reply to this post here on OGA.