Can't play portal 2 sounds in console!

The error comes out as


Failed to load sound "[portal 2 sound]", file probably missing from disk/repository

I have searched for the problem, but I don’t understand the solutions I have read.

How do I fix it?

could anyone tell me what they were talking about in this thread?

http://forum.facepunch.com/showthread.php?t=1199220

The thread refers to using Portal 2 sounds pre-mounting, however, I believe Valve changed the sound format since then to where the sounds wouldn’t work either way in Garry’s Mod.