It could be other sound editor software too but in this step I'm gonna using Audacity.
Download Link [www.audacityteam.org]


Make sure to tick the tools checkbox in ur library to see the software, then simply go install it.

Or click here in case link above can't play the video
Youtube Link











1. Make sure you know which sound file for which sound in-game. For example if u want to editing spray sound in-game, then u can take a look in ur l4d2 folder->Sound->Player->Sprayer.wav. If u want to editing your Tank attacking sound, then u can search in ur l4d2 folder->Sound->Player->Tank->Attack->rip_up_rock_1.wav.

If u don't know where to find the sound that you want to change, u can try searching for the sound you looking for in the in the community first, then go to l4d2->addons->workshop and search the one that you just subbed, open the vpk file with software like GFScape or any, then take a look at the folder structures, then u will know where the file location.


2. Open the Audacity, drag the original file that you want to edit, also the sound file you want to change into(It could be something like a sound effect from Youtube, or any file).

Or maybe you want to pick it from any movie line, then u can cut the movie first and then get the voice line that you want, idk it's up to you where to get the voice line, your creativity.

My tips if u want download something from youtube just add "ss" in the beginning of the url. So from "https://www.youtube.com/watch?v=aaaaa" to "https://www.ssyoutube.com/watch?v=aaaaa", and u will be directed to the download site.


3. After u hab both the original file and the sound u want to change into in Audacity, then all u need is to pay attention to 2 things.

The Length
Make sure to edit the voice line so that you have exactly the same length as the original file. Not too short, not too long, but exactly the same length.

So u need to turn this:


Into This:

Do whatever you want, increase the volume, cut the parts u want, edit it as to your liking.

The Hertz
Before you exporting as WAV, make sure to pick the same Hz as the original file, in this case the Hz is 22Hz, but the sound file is 44 Hz, so make sure to pick the right Hz on the bottom left Check-list box.


Lastly, don't forget to Silence the original sound file, just drag all the original sound go to generate tab, and pick silence. This step is so that you guys only hear the edited sound you want, not the original sound anymore, cuz it's gonna be weird when you hear 2 sounds playing at once.


After u done then just export as WAV and make sure to export it as the original file name.wav.

After u have done creating the WAV files, then you just need to create it into VPK.
Here is where you need to pay attention
Create another folder path that is exactly the same as the original file. For example if u editing the hulk_punch_1 file then create a folder just like where the hulk_punch_1 located in.


Then go create another folder in ur desktop or wherever u want like this


After that add some notepad file named "addoninfo".txt


Just copy everything after this text(Including the "AddonInfo"):

"AddonInfo"
{
addonSteamAppID "550"
addontitle "Your Mod VPK title"
addonversion "1"
addonauthor "Your name"
addonauthorSteamID ""
addonURL0 ""
addonDescription "The Description which u can see in game add-ons menu"
}


And for the blank or number part just leave it as it is.

After u got ur folder done. Just simply go to l4d2->bin->vpk.exe

U can copy paste the vpk.exe to deskstop so it's easier to use but the main point is just to simply drag the folder that u have created into the vpk.exe. And then u should see ur vpk file named as ur folder name.



All is done..then what left is just to uploading to workshop if u want, go launch the l4d2 authoring tool app, go to Workshop Manager, fill the things, and done.

Or maybe you want to test your mod first, then simply copy ur vpk file into l4d2->l4d2->addons and paste it there. U can test it first maybe the volume too big or too low or whatever.


That's it. Hope u guys can understand it, I honestly prefer to watch the youtube video if u guys don't like reading a wall of text, anyway enjoy and be creative with it.