Minecraft now uses another path to sounds, the sound folder now is called "sounds" instead "sound". My launcher has downloaded some sounds into "sounds" folder for new snapshot, but some folders like "random" or "tile" are missing. And another great problem - old resource packs do not replace sounds
Please, rename back "sounds" folder into "sound" in the game paths.
How to reproduce:
1) Download snapshot 13w42a
2) Set sounds to 100%
3) Shoot an arrow / Activate a piston / Explode a TNT / Use a potion
4) Enjoy the silence............