Hello recently I have been trying to put the rebel sound’s from hl2 into hl1, now I know what your thinking but just let me say, I am using these sound’s for my own personal use. Anyway I convert the sound’s in audacity to 11025hz and they work in half-life but the characters mouths will not move. How do I fix this problem? Can anyone help me with this problem? Please and thank you. 
They must be 8-bit mono sounds as well. That should work for you.
okay I will try that.
problem there is no 8bit- sound option lowest is 16 bit what do I do?
Get a new sound editor. 
I have commercial software, so I don’t know what free stuff you could get.
do you know any good free one’s?
Well audacity is the best free one. Try looking for a add-on for audacity or investigate if the SDK contains a converter.
I still can’t do it and I did what you said. EDIT: also what do you use Jeffmod
You can set it 8 bit in Audacity, in the File Formats tab in Preferences.
Never mind it works now thanks.
Good to see it’s fixed.
I, personally use Sony Sound Forge Audio Studio 9.0, and it’s fairly good for it’s pricetag, if a bit old now. Even comes with a CD of 1000 sound FX, though I’ve yet to use one.