How to adjust the volume of a mod's custom sounds?

[Mark]

All I have to do is shout "KOMATSU" and most people will know what I'm talking about.
Some mods have custom sounds. Some of those sounds are loud as hell, or glitched and can be heard no matter how far away you are.

On the other hand you have the Audi 80 Quattro which is somehow whisper quiet, compared to normal vehicles, when revving at 8k

How can I modify these, to adjust the volume of their custom sounds? either to make them quieter, or louder?

 

[LogWhat1]

This is a problem I've been experiencing. When someone spawns that KOMATSU bulldozer, my eardrums explode.
But there is this in the soundscript.

(SS from 2016 Bluebird All American T3FE School Bus)

 

[Mark]

I tried adding these two lines to the soundscript file in the engine idle section, didn't make any difference (probably doesn't help that I don't know what I'm doing)
I read some of the Docs on this stuff but don't really understand it

I tried making the actual .wav file louder, and I did, but in game it is the same volume it was

Good guess though