It was built into whichever voice-chat software we were using, just a simple right-click action. This was a long time ago, so I don't totally remember, probably 2008-2012 or so? Trying to jog my memory with Google and I think it was TeamSpeak and the "3D Sound" feature. I feel like Mumble may also have been able to do this.

That's a really cool idea, thanks for the heads up. Didn't realize it was possible but man would it make a world of difference in meetings.