Nonono my friend, look no further.
The grenade effect master, diamond-optic, has already conquered this mountain in DoD Shellshock:
http://dodplugins.net/forums/showthread.php?t=56
Check out his code for the volume stuff. It drops your volume level and even gives you this crazy effect where it seems like the footsteps are all around you and you literally feel dizzy. I don't even know how he does it; but it's in the code.
EDIT: and yeah, it's friggin compatible with your mod..cs, ts, BS, whatever
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