As I do not have Reloaded, I'm assuming that based on DarkGDK's "3D Sound" and from what I've glanced in this forum about 3D Sound - that whatever 3D sound that is present (if it is present), I'm assuming it's just volume based: A sound that comes from the player's right is a little louder on the right.
My suggestion is to add a slight delay to the further-away side. In the real world, a sound coming from the player's right will arrive at the left ear slighter after it arrives at the right ear.
And give the game-author the ability to scale the left/right volume ratio, and the phase delay. Giving separate control to each aspect (with some good sounding defaults in place to start with of course). They'd each be calculated from the angle of the sound relative to the player, of course, then scaled by the game-author's settings.
The phase delay is more of a time delay in this case, a simple delay of playback by a number of samples, calculated from the delay time and sampling rate. To make things simpler, you could even round it to the nearest integer sample.
I've uploaded a panting zombie sound as a sample to illustrate the difference it makes. The original sound was mono (stereo but identical channels), and authored by Duncan Peck, which he shared in the following thread:
http://fpscrforum.thegamecreators.com/?m=forum_view&t=208431&b=25
This sample is from a stationary position. But imagine it changing as the zombie moves closer.
The original sound (effectively mono):
hahahuh - Original.wav
The sound coming from the right, using a change of volume only:
hahahuh - Volume only.wav
The sound coming from the right, using a delay only:
hahahuh - Delay only.wav
The sound coming from the right, using both the volume and delay (same settings as above):
hahahuh - Volume and Delay.wav
Note: These above four files are the attachments. No need to download them twice.
