i made a video about this but people complained its low quality so i made this guide! but you can still watch if u want..

First thing is that you'll need audacity and the L4D2 authoring tools installed, so go download them.














Next you'll go to wherever your sound folder and choose whatever you wanna mod, so for me it'll be "D:\SteamLibrary\steamapps\common\Left 4 Dead 2\left4dead2\sound\weapons\rifle"






Next you'll copy the folder you're modding so copy whats in between the lines "left4dead2\-sound\mainsoundfolder\folderyoullbemodding\folderscontainingsounds-" the mod folder should be structured like this:

Now you'll wanna open the sound you wanna mod in audacity, then drag the sound that'll replace it in audacity

Next you'll edit the replacing sound follow the image below for instructions (if you don't know how to change mono to stereo, 4423402z or float, idk either look it up on youtube :3)
After you're done editing the audio, you'll wanna delete the og audio in audacity, export it to the sound folder of your mod folder and replace the sound file (see image below)
After editing your audio, go to your mod folder and create a text file with the name "addoninfo" and copy this into it

"AddonInfo"
{
addonSteamAppID 550
addontitle "mod name goes here!"
addonversion 1
addonauthor "your name goes here!!"
addonDescription "something idk"
}

it should look like this

(OPTIONAL)
addonimage.jpg is the thumbnail for your addon that will appear -IN-GAME- the real thumbnail will be added in the uploading process.






i recomend putting your mod folder in the addons folder already for convenience

After intalling the L4D2 authoring tools, "vpk.exe" should appear in "D:\SteamLibrary\steamapps\common\Left 4 Dead 2\bin". You'll use it to turn your folder into a vpk file.

After all of that, launch your game to test it out!

To upload your mod, open the L4D2 authoring tools, go to workshop manager, click the plus sign and fill out all of the requirements and click upload!
and that's it. you're done.

You WILL give me awards You WILL give me all your steam points