Due to the limitations of GoldSource, the game can't handle more than 22050 Hz audio and if there's an audio file that has higher bitrate than 22050 Hz, the game will play them in very poor quality. So, this mod fixes it.
I just downgraded the 44.1 khz audio files to 11.25 and 22.5 khz audio so they can play properly without lowering the audio quality that much.
If you playing it on Xash3D, you don't need this mod as Xash3D can handle audio files beyond 22.5 khz.
Installation: just put the "sound" folder to your field intensity mod folder and it will replace the sound files
(FOR STEAM VERSION) If you don't want to replace any file, just create a folder named "field_intensity_addon" in your Half-Life directory and place the "sound" folder there and make sure "Enable custom addon content" enabled in the game settings.
Programs used:
Audacity
Goldwave (since Audacity can't put cue points as cue points required for audio looping, I had to use this software to put cue points)