Go to your C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod and delete both that addons, and the sound folder, then re-launch garrys mod and let it do it's magic.
If there is no sound folder, then delete the garrysmod_dir.vpk file in your garrysmod folder. I highlight this red because this is a last resort thing, because this contains all the information gmod needs. Once you delete it, verify your game files.
If you do not know how to verify your game files
Go to your steam game library
Right click on garrys mod
Click on properties
Go to local files tab
Verify integrity of game files
Let me know if this fixes your issues.
Any more issues are likely cause to:
Another conflicting addon
Corrupt gmod (requires complete reinstall)
File downloads incorrectly (for this, contact me on teamspeak or something and I will give you any further steps)