Everything audio in Homeworld is first compressed using the aifr codec from Relic. This is included in the hwss toolkit. HWSS won't even start unless you've installed the NCT audio editor OCX. It can be found from:
nctsoft

Start HWSS, click the Convert button on the left. This will change the view window (right side) to show the conversion functions.

Click the wav->aifr tab. The view will further change. On the left side, set the directory where your wav files are stored. The right side will list any wav files there. Set the encoding bitrate with the drop list (middle) and hit the button to start encoding. The bottom section will show some debug output so you can know what will happen.

The program will pop up some dos windows while it is encoding each file. The main program may behave like it is locked up until it is finished encoding each wav file in the list. This is normal. The dos windows should disappear on their own. If not, close them when the encoding is done.

The aifr files should now appear in the same directory as the wav files. Each will also have an associated LOG file. These log files are VERY important, please leave them alone.

NOTE: Each wav file must have a playback time of at LEAST 1 second, or the relic encoder will produce an empty file. You can use a program like Goldwave32 to extend or add silence to a sound file that is less than 3 seconds in playback time.