Well i faced with your problems few days ago. I tried to import some dota2's sounds into my map.
-First thing to mention, it was 44100 Hz, 16 bit, Strereo. Of course it work, but isnt a 3D sound, so once you played it with trigger, it actually will be turned into global sound which means you can hear it anywhere. 3D sound does provide more things than normal sound does, if you want to turn a sound in to 3D sound, it must be xxxx(x) Hz, 16 bits, Mono MUST BE 16 bit and MONO in order to work as a 3D sound otherwise is not going to work in game and with that quality, its like shit (for me). I did try to turn it into mp3 and use that as a sound but it wasnt a 3D sound. Well i think the only way to turn a sound into 3D is with a sound edtior (in my case: Wavepad Sound Editor), and save it in .wav or .mp3 with xxxx(x) Hz, 16 bits, Mono