There are few sounds as sedate as that of rain — except, perhaps, a sample of rain recorded in the city of Utrecht to which is applied “the EVOC filterbank (vocoder) from Logic Pro to filter the sound file in a study of noise-filtering.”
That’s what a user who goes by thanvannispen did at the open-source field recording website, freesound.iua.upf.edu: he first recorded the rain and posted the file, in all its 39 seconds of precipitate beauty (MP3), and he then remixed the sound and posted the modified version (MP3) to the ever-flowering “remix tree” section of the freesound website. The result is a deep, resonant background noise, one that plays for about 50 percent longer than the original. For higher quality audio, additional data on the sounds, and visualizations, you can check out the before and after sounds’ individual pages (first, second).
Now, thanvannispen (or Than van Nispen) is something a star among the field recorders who’ve posted some 37,838 sound files (as of this writing) at freesound. Why? Because his “maleThijsloud_scream” (MP3, page) was used in the film Children of Men. Seriously. It’s listed just below Aphex Twin in the movie’s credits, a still from which is reproduced on van Nispen’s personal website at the Utrecht School of the Arts (student-kmt.hku.nl/~than). Scroll down on that freesound page to learn more about the use of the sound in the movie, and to read the praise of his fellow field recorders.