Sounds

Impersonator -> The program you can use to generate LTF files

While we may not have a working sound import command for Halo 2, that doesn't mean we don't have any sound functionality in our toolset. One leftover command that you may find interesting is a command by the name of import-lipsync. As the name implies this command allows the user to add lipsync data to existing sound files. The result from this being mouth movement to go with your sound obviously. You will find the program you need to do this in the above links. The program "Impersonator" is what you will use to generate the LTF files from compatible WAV and AIFF files.

For custom sounds you can import them using tool.exe from Halo CE's HEK using the Xbox codec. Make sure to resave the sound before using the command as it will not work otherwise. Refer to the manual that comes with Impersonator for instructions on how to generate LTF files from it.