Directory structure as following:

Level Name (Directory)
  |
  ---s01.wav (Sound Effects - 3D Sound)
  |
  ---s02.wav
  |
  ---...
  |
  ---t01.wav (Background Music - no 3D Sound)
  |
  ---t02.wav
  |
  ---...


WAV-Files should be 44100kHz and 16bits by default.
Sound Effects have to contain only 1 Channel (Mono). Because only Mono-WAVs can be positioned.
Background Music should preferrably be Stereo because they won't be positioned in the world.