MumbleLink enables positional audio support in the voice chat program Mumble, allowing anyone using the mod in multiplayer and in the same voice channel to hear one another spatially in 3D - meaning you can make out their direction relative to you and, if so configured, hear them quieter depending on how far away they are. The mod is completely client-side, so you can use it on any server you wish.
[ VSModDB ] [ GitHub Releases ] Source code and information on how to set it up are also available on GitHub.