Does anyone know where I can find costum soundsets for units

[Dreadzylocks]

soundsets that aren't in the actual game.

 

[NightSkyAurora]

Wc3Underground

 

[WaterKnight]

You cannot really have own soundsets in a map without mpq modification. And by soundsets I mean the setup that parks paths of single sounds under keys and the soundset identifier. You can only replace the sound paths of existing soundsets.