No, not really a "pak", just a "pack" of files I guess, nicely downloadable in a small zip.
What? Some of you may remember it from a long time ago... what it does is shutup the loud looped ambient sound(s) in SiNCity, Dm6, and Oilrig. That includes wind, city sfx, and machinery.
Why? Well, those loud looped sounds in those levels drown out the player and battle action sounds, or they just generally distract you at times. They add to the immersion experience, but once you get down to it, you'd rather have one or two more frags in the end, eh?
When? Silencer was released a long time ago, during first months of initial SiN full release. It was just SiNCity and Dm6 then, no Oilrig.
How? Nothing special or complicated, I simply made a mute wav file (0.5 sec, 3kb). Then I went to each of the "noisy" levels, condumped a soundlist. Then unpak'd pak0.sin (has sfx) into a temporary dir outside of base, found the questionable sfx wav's and made note of their file and dir names. Created a sin\base\sounds\environment\ dir, and appropriately created the dir's, and then ctrl+v'ing mute.wav and re-naming it to the correct wav files. What happens is when the map loads, the pak's are scanned for the needed files first, then the directories in sin\base\, so it will hit those new muted wav's and use them instead of the originals in the .pak files.
Where? Here: http://www.urbanwarfare.com/sin_silencer.zip
. It's a 7kb zip file. Unzip it into sin\base\sounds\, keeping the sub-dirs on.
Silencer doesn't overwrite anything. If you don't want it anymore, just simply move sin\base\sounds\environment\ somewhere else, or delete it if you want it away for good.
I find playing in SiNCity, Dm6, and Oilrig easier, because you can hear everything thats going on with all the players.