Attenuation
Also said as Falloff, Rolloff, Distance curve
How a sound gets quieter as you move away from it. A curve maps distance to volume, usually with a range inside which it is at full volume and a range beyond which it stops.
Attenuation is how players locate things by ear. The curve is a design choice, not physics: an important enemy can be audible from further than reality would allow.
Say it
“Enemy footsteps stay at full volume to 3 m, fall off on an inverse curve, and stop at 25 m. Distant footsteps should still be locatable.”
Where you’ve seen it
Overwatch departs from realism on purpose: enemy footsteps are mixed louder than allies' footsteps, because they matter more. Its designers described this at GDC in 2016.
Not to be confused with occlusion
Attenuation depends only on distance. Occlusion is what happens when something solid stands in between.