KanecoSo there's really no way to remove the killstreak sound?
Not that I can tell. I think I may have found the way to replace it after looking into the files.
The sound that the game makes when a killstreak is active is called killstreak.wav. So, if you wanted to replace it, your folder/file directory should look something like
SteamApps\common\Team Fortress 2\tf\<your custom folder>\sound\misc\killstreak.wav
So all you need to do is create a blank audio file, name it killstreak.wav and it should override the usual loud noise. However, I've never messed with sound files before so I could be wrong. Someone can correct me if needs be.