This was added in e3e5bd1 as a work around for some openal-soft bug.
When too many audio samples got played at the same time, the global
volume dropped. This was fixed in openal-soft 0.19.0, released more
than two years ago. We're keeping the work around, because some
distros may still ship with buggy openal-soft versions and some
players may like the changed behavior. It's disabled by default.
If too many of these sounds are started in one frame (for example if the
player shoots with the super shotgun into the power screen of a Brain)
things get too loud and OpenAL is forced to scale the volume of several
other sounds and the background music down. That leads to a noticable
and annoying drop in the overall volume.
Work around that by limiting the number of sounds started. 16 was
choosen by empirical testing.
