After some laborious web searching, I found it.
Go to this thread in another forum:
http://forum.macologist.org/showthread.php?t=308&page=2
It will point you to this download:
[link removed, no longer available]
Be sure to take the Intel-compiled version.
Follow the instructions from the forum post:
1. Download it and unzip it.
2. Open the dir 'Unreal Tournament 2004.app/System/'
3. Rename your rename your old 'OpenAL.dylib' to 'OpenAL.dylib_Old'
4. Drop in the new one.
That's it. I've played a standard botmatch in Antalus on my new MacBook Pro 4, 2.5 GHz, and all sounds, including rude taunts, are back. The sound balance seems subtly different - weapons and ammo "pickup" ques are a little softer I think. It may have something to do with the fact that this rebuild of the game's OpenAL interface implements surround-sound. I'm going to search around a little in the config files to see if there is access to control that.
I miss my favorite female voice taunt from UT 99 though: "I'm sorry. Did I just blow your head off?"
Enjoy!
Edit:
O yes.
After adding the new "OpenAL.dylib" to your "Unreal Tournament 2004.app/System/" folder, go over to "<home>/Library/Application Support/Unreal Tournament 2004/" and edit "UT2004.ini":
[ALAudio.ALAudioSubsystem]
UseEAX=True
Use3DSound=True
Instant environmental sound goodness!
Wow. The sound of footsteps placed exactly correctly as your teammates speed past you. I fragged a guy with the Flack Cannon in a narrow canyon opening in Antalus and I could here the sloppy wet bounces of his frags off the walls in all the right locations on both sides of me.
That is on headphones (I'm late at the office right now). I'm sure that those of you with elaborate 5.1 systems are going to have a lot of fun. Just don't end up divorced!
Enjoy!